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1 : : /*-------------------------------------------------------------------------
2 : : *
3 : : * bufmgr.c
4 : : * buffer manager interface routines
5 : : *
6 : : * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
7 : : * Portions Copyright (c) 1994, Regents of the University of California
8 : : *
9 : : *
10 : : * IDENTIFICATION
11 : : * src/backend/storage/buffer/bufmgr.c
12 : : *
13 : : *-------------------------------------------------------------------------
14 : : */
15 : : /*
16 : : * Principal entry points:
17 : : *
18 : : * ReadBuffer() -- find or create a buffer holding the requested page,
19 : : * and pin it so that no one can destroy it while this process
20 : : * is using it.
21 : : *
22 : : * StartReadBuffer() -- as above, with separate wait step
23 : : * StartReadBuffers() -- multiple block version
24 : : * WaitReadBuffers() -- second step of above
25 : : *
26 : : * ReleaseBuffer() -- unpin a buffer
27 : : *
28 : : * MarkBufferDirty() -- mark a pinned buffer's contents as "dirty".
29 : : * The disk write is delayed until buffer replacement or checkpoint.
30 : : *
31 : : * See also these files:
32 : : * freelist.c -- chooses victim for buffer replacement
33 : : * buf_table.c -- manages the buffer lookup table
34 : : */
35 : : #include "postgres.h"
36 : :
37 : : #include <sys/file.h>
38 : : #include <unistd.h>
39 : :
40 : : #include "access/tableam.h"
41 : : #include "access/xloginsert.h"
42 : : #include "access/xlogutils.h"
43 : : #ifdef USE_ASSERT_CHECKING
44 : : #include "catalog/pg_tablespace_d.h"
45 : : #endif
46 : : #include "catalog/storage.h"
47 : : #include "catalog/storage_xlog.h"
48 : : #include "executor/instrument.h"
49 : : #include "lib/binaryheap.h"
50 : : #include "miscadmin.h"
51 : : #include "pg_trace.h"
52 : : #include "pgstat.h"
53 : : #include "postmaster/bgwriter.h"
54 : : #include "storage/aio.h"
55 : : #include "storage/buf_internals.h"
56 : : #include "storage/bufmgr.h"
57 : : #include "storage/fd.h"
58 : : #include "storage/ipc.h"
59 : : #include "storage/lmgr.h"
60 : : #include "storage/proc.h"
61 : : #include "storage/proclist.h"
62 : : #include "storage/read_stream.h"
63 : : #include "storage/smgr.h"
64 : : #include "storage/standby.h"
65 : : #include "utils/memdebug.h"
66 : : #include "utils/ps_status.h"
67 : : #include "utils/rel.h"
68 : : #include "utils/resowner.h"
69 : : #include "utils/timestamp.h"
70 : :
71 : :
72 : : /* Note: these two macros only work on shared buffers, not local ones! */
73 : : #define BufHdrGetBlock(bufHdr) ((Block) (BufferBlocks + ((Size) (bufHdr)->buf_id) * BLCKSZ))
74 : : #define BufferGetLSN(bufHdr) (PageGetLSN(BufHdrGetBlock(bufHdr)))
75 : :
76 : : /* Note: this macro only works on local buffers, not shared ones! */
77 : : #define LocalBufHdrGetBlock(bufHdr) \
78 : : LocalBufferBlockPointers[-((bufHdr)->buf_id + 2)]
79 : :
80 : : /* Bits in SyncOneBuffer's return value */
81 : : #define BUF_WRITTEN 0x01
82 : : #define BUF_REUSABLE 0x02
83 : :
84 : : #define RELS_BSEARCH_THRESHOLD 20
85 : :
86 : : /*
87 : : * This is the size (in the number of blocks) above which we scan the
88 : : * entire buffer pool to remove the buffers for all the pages of relation
89 : : * being dropped. For the relations with size below this threshold, we find
90 : : * the buffers by doing lookups in BufMapping table.
91 : : */
92 : : #define BUF_DROP_FULL_SCAN_THRESHOLD (uint64) (NBuffers / 32)
93 : :
94 : : /*
95 : : * This is separated out from PrivateRefCountEntry to allow for copying all
96 : : * the data members via struct assignment.
97 : : */
98 : : typedef struct PrivateRefCountData
99 : : {
100 : : /*
101 : : * How many times has the buffer been pinned by this backend.
102 : : */
103 : : int32 refcount;
104 : :
105 : : /*
106 : : * Is the buffer locked by this backend? BUFFER_LOCK_UNLOCK indicates that
107 : : * the buffer is not locked.
108 : : */
109 : : BufferLockMode lockmode;
110 : : } PrivateRefCountData;
111 : :
112 : : typedef struct PrivateRefCountEntry
113 : : {
114 : : /*
115 : : * Note that this needs to be same as the entry's corresponding
116 : : * PrivateRefCountArrayKeys[i], if the entry is stored in the array. We
117 : : * store it in both places as this is used for the hashtable key and
118 : : * because it is more convenient (passing around a PrivateRefCountEntry
119 : : * suffices to identify the buffer) and faster (checking the keys array is
120 : : * faster when checking many entries, checking the entry is faster if just
121 : : * checking a single entry).
122 : : */
123 : : Buffer buffer;
124 : :
125 : : PrivateRefCountData data;
126 : : } PrivateRefCountEntry;
127 : :
128 : : /* 64 bytes, about the size of a cache line on common systems */
129 : : #define REFCOUNT_ARRAY_ENTRIES 8
130 : :
131 : : /*
132 : : * Status of buffers to checkpoint for a particular tablespace, used
133 : : * internally in BufferSync.
134 : : */
135 : : typedef struct CkptTsStatus
136 : : {
137 : : /* oid of the tablespace */
138 : : Oid tsId;
139 : :
140 : : /*
141 : : * Checkpoint progress for this tablespace. To make progress comparable
142 : : * between tablespaces the progress is, for each tablespace, measured as a
143 : : * number between 0 and the total number of to-be-checkpointed pages. Each
144 : : * page checkpointed in this tablespace increments this space's progress
145 : : * by progress_slice.
146 : : */
147 : : float8 progress;
148 : : float8 progress_slice;
149 : :
150 : : /* number of to-be checkpointed pages in this tablespace */
151 : : int num_to_scan;
152 : : /* already processed pages in this tablespace */
153 : : int num_scanned;
154 : :
155 : : /* current offset in CkptBufferIds for this tablespace */
156 : : int index;
157 : : } CkptTsStatus;
158 : :
159 : : /*
160 : : * Type for array used to sort SMgrRelations
161 : : *
162 : : * FlushRelationsAllBuffers shares the same comparator function with
163 : : * DropRelationsAllBuffers. Pointer to this struct and RelFileLocator must be
164 : : * compatible.
165 : : */
166 : : typedef struct SMgrSortArray
167 : : {
168 : : RelFileLocator rlocator; /* This must be the first member */
169 : : SMgrRelation srel;
170 : : } SMgrSortArray;
171 : :
172 : : /* GUC variables */
173 : : bool zero_damaged_pages = false;
174 : : int bgwriter_lru_maxpages = 100;
175 : : double bgwriter_lru_multiplier = 2.0;
176 : : bool track_io_timing = false;
177 : :
178 : : /*
179 : : * How many buffers PrefetchBuffer callers should try to stay ahead of their
180 : : * ReadBuffer calls by. Zero means "never prefetch". This value is only used
181 : : * for buffers not belonging to tablespaces that have their
182 : : * effective_io_concurrency parameter set.
183 : : */
184 : : int effective_io_concurrency = DEFAULT_EFFECTIVE_IO_CONCURRENCY;
185 : :
186 : : /*
187 : : * Like effective_io_concurrency, but used by maintenance code paths that might
188 : : * benefit from a higher setting because they work on behalf of many sessions.
189 : : * Overridden by the tablespace setting of the same name.
190 : : */
191 : : int maintenance_io_concurrency = DEFAULT_MAINTENANCE_IO_CONCURRENCY;
192 : :
193 : : /*
194 : : * Limit on how many blocks should be handled in single I/O operations.
195 : : * StartReadBuffers() callers should respect it, as should other operations
196 : : * that call smgr APIs directly. It is computed as the minimum of underlying
197 : : * GUCs io_combine_limit_guc and io_max_combine_limit.
198 : : */
199 : : int io_combine_limit = DEFAULT_IO_COMBINE_LIMIT;
200 : : int io_combine_limit_guc = DEFAULT_IO_COMBINE_LIMIT;
201 : : int io_max_combine_limit = DEFAULT_IO_COMBINE_LIMIT;
202 : :
203 : : /*
204 : : * GUC variables about triggering kernel writeback for buffers written; OS
205 : : * dependent defaults are set via the GUC mechanism.
206 : : */
207 : : int checkpoint_flush_after = DEFAULT_CHECKPOINT_FLUSH_AFTER;
208 : : int bgwriter_flush_after = DEFAULT_BGWRITER_FLUSH_AFTER;
209 : : int backend_flush_after = DEFAULT_BACKEND_FLUSH_AFTER;
210 : :
211 : : /* local state for LockBufferForCleanup */
212 : : static BufferDesc *PinCountWaitBuf = NULL;
213 : :
214 : : /*
215 : : * Backend-Private refcount management:
216 : : *
217 : : * Each buffer also has a private refcount that keeps track of the number of
218 : : * times the buffer is pinned in the current process. This is so that the
219 : : * shared refcount needs to be modified only once if a buffer is pinned more
220 : : * than once by an individual backend. It's also used to check that no
221 : : * buffers are still pinned at the end of transactions and when exiting. We
222 : : * also use this mechanism to track whether this backend has a buffer locked,
223 : : * and, if so, in what mode.
224 : : *
225 : : *
226 : : * To avoid - as we used to - requiring an array with NBuffers entries to keep
227 : : * track of local buffers, we use a small sequentially searched array
228 : : * (PrivateRefCountArrayKeys, with the corresponding data stored in
229 : : * PrivateRefCountArray) and an overflow hash table (PrivateRefCountHash) to
230 : : * keep track of backend local pins.
231 : : *
232 : : * Until no more than REFCOUNT_ARRAY_ENTRIES buffers are pinned at once, all
233 : : * refcounts are kept track of in the array; after that, new array entries
234 : : * displace old ones into the hash table. That way a frequently used entry
235 : : * can't get "stuck" in the hashtable while infrequent ones clog the array.
236 : : *
237 : : * Note that in most scenarios the number of pinned buffers will not exceed
238 : : * REFCOUNT_ARRAY_ENTRIES.
239 : : *
240 : : *
241 : : * To enter a buffer into the refcount tracking mechanism first reserve a free
242 : : * entry using ReservePrivateRefCountEntry() and then later, if necessary,
243 : : * fill it with NewPrivateRefCountEntry(). That split lets us avoid doing
244 : : * memory allocations in NewPrivateRefCountEntry() which can be important
245 : : * because in some scenarios it's called with a spinlock held...
246 : : */
247 : : static Buffer PrivateRefCountArrayKeys[REFCOUNT_ARRAY_ENTRIES];
248 : : static struct PrivateRefCountEntry PrivateRefCountArray[REFCOUNT_ARRAY_ENTRIES];
249 : : static HTAB *PrivateRefCountHash = NULL;
250 : : static int32 PrivateRefCountOverflowed = 0;
251 : : static uint32 PrivateRefCountClock = 0;
252 : : static int ReservedRefCountSlot = -1;
253 : : static int PrivateRefCountEntryLast = -1;
254 : :
255 : : static uint32 MaxProportionalPins;
256 : :
257 : : static void ReservePrivateRefCountEntry(void);
258 : : static PrivateRefCountEntry *NewPrivateRefCountEntry(Buffer buffer);
259 : : static PrivateRefCountEntry *GetPrivateRefCountEntry(Buffer buffer, bool do_move);
260 : : static inline int32 GetPrivateRefCount(Buffer buffer);
261 : : static void ForgetPrivateRefCountEntry(PrivateRefCountEntry *ref);
262 : :
263 : : /* ResourceOwner callbacks to hold in-progress I/Os and buffer pins */
264 : : static void ResOwnerReleaseBufferIO(Datum res);
265 : : static char *ResOwnerPrintBufferIO(Datum res);
266 : : static void ResOwnerReleaseBuffer(Datum res);
267 : : static char *ResOwnerPrintBuffer(Datum res);
268 : :
269 : : const ResourceOwnerDesc buffer_io_resowner_desc =
270 : : {
271 : : .name = "buffer io",
272 : : .release_phase = RESOURCE_RELEASE_BEFORE_LOCKS,
273 : : .release_priority = RELEASE_PRIO_BUFFER_IOS,
274 : : .ReleaseResource = ResOwnerReleaseBufferIO,
275 : : .DebugPrint = ResOwnerPrintBufferIO
276 : : };
277 : :
278 : : const ResourceOwnerDesc buffer_resowner_desc =
279 : : {
280 : : .name = "buffer",
281 : : .release_phase = RESOURCE_RELEASE_BEFORE_LOCKS,
282 : : .release_priority = RELEASE_PRIO_BUFFER_PINS,
283 : : .ReleaseResource = ResOwnerReleaseBuffer,
284 : : .DebugPrint = ResOwnerPrintBuffer
285 : : };
286 : :
287 : : /*
288 : : * Ensure that the PrivateRefCountArray has sufficient space to store one more
289 : : * entry. This has to be called before using NewPrivateRefCountEntry() to fill
290 : : * a new entry - but it's perfectly fine to not use a reserved entry.
291 : : */
292 : : static void
293 : 11430862 : ReservePrivateRefCountEntry(void)
294 : : {
295 : : /* Already reserved (or freed), nothing to do */
296 [ + + ]: 11430862 : if (ReservedRefCountSlot != -1)
297 : 10001149 : return;
298 : :
299 : : /*
300 : : * First search for a free entry the array, that'll be sufficient in the
301 : : * majority of cases.
302 : : */
303 : : {
304 : 1429713 : int i;
305 : :
306 [ + + ]: 12867417 : for (i = 0; i < REFCOUNT_ARRAY_ENTRIES; i++)
307 : : {
308 [ + + ]: 11437704 : if (PrivateRefCountArrayKeys[i] == InvalidBuffer)
309 : : {
310 : 8900598 : ReservedRefCountSlot = i;
311 : :
312 : : /*
313 : : * We could return immediately, but iterating till the end of
314 : : * the array allows compiler-autovectorization.
315 : : */
316 : 8900598 : }
317 : 11437704 : }
318 : :
319 [ + + ]: 1429713 : if (ReservedRefCountSlot != -1)
320 : 1421696 : return;
321 [ - + + ]: 1429713 : }
322 : :
323 : : /*
324 : : * No luck. All array entries are full. Move one array entry into the hash
325 : : * table.
326 : : */
327 : : {
328 : : /*
329 : : * Move entry from the current clock position in the array into the
330 : : * hashtable. Use that slot.
331 : : */
332 : 8017 : int victim_slot;
333 : 8017 : PrivateRefCountEntry *victim_entry;
334 : 8017 : PrivateRefCountEntry *hashent;
335 : 8017 : bool found;
336 : :
337 : : /* select victim slot */
338 : 8017 : victim_slot = PrivateRefCountClock++ % REFCOUNT_ARRAY_ENTRIES;
339 : 8017 : victim_entry = &PrivateRefCountArray[victim_slot];
340 : 8017 : ReservedRefCountSlot = victim_slot;
341 : :
342 : : /* Better be used, otherwise we shouldn't get here. */
343 [ + - ]: 8017 : Assert(PrivateRefCountArrayKeys[victim_slot] != InvalidBuffer);
344 [ + - ]: 8017 : Assert(PrivateRefCountArray[victim_slot].buffer != InvalidBuffer);
345 [ + - ]: 8017 : Assert(PrivateRefCountArrayKeys[victim_slot] == PrivateRefCountArray[victim_slot].buffer);
346 : :
347 : : /* enter victim array entry into hashtable */
348 : 16034 : hashent = hash_search(PrivateRefCountHash,
349 : 8017 : &PrivateRefCountArrayKeys[victim_slot],
350 : : HASH_ENTER,
351 : : &found);
352 [ + - ]: 8017 : Assert(!found);
353 : : /* move data from the entry in the array to the hash entry */
354 : 8017 : hashent->data = victim_entry->data;
355 : :
356 : : /* clear the now free array slot */
357 : 8017 : PrivateRefCountArrayKeys[victim_slot] = InvalidBuffer;
358 : 8017 : victim_entry->buffer = InvalidBuffer;
359 : :
360 : : /* clear the whole data member, just for future proofing */
361 : 8017 : memset(&victim_entry->data, 0, sizeof(victim_entry->data));
362 : 8017 : victim_entry->data.refcount = 0;
363 : 8017 : victim_entry->data.lockmode = BUFFER_LOCK_UNLOCK;
364 : :
365 : 8017 : PrivateRefCountOverflowed++;
366 : 8017 : }
367 : 11430862 : }
368 : :
369 : : /*
370 : : * Fill a previously reserved refcount entry.
371 : : */
372 : : static PrivateRefCountEntry *
373 : 10641775 : NewPrivateRefCountEntry(Buffer buffer)
374 : : {
375 : 10641775 : PrivateRefCountEntry *res;
376 : :
377 : : /* only allowed to be called when a reservation has been made */
378 [ + - ]: 10641775 : Assert(ReservedRefCountSlot != -1);
379 : :
380 : : /* use up the reserved entry */
381 : 10641775 : res = &PrivateRefCountArray[ReservedRefCountSlot];
382 : :
383 : : /* and fill it */
384 : 10641775 : PrivateRefCountArrayKeys[ReservedRefCountSlot] = buffer;
385 : 10641775 : res->buffer = buffer;
386 : 10641775 : res->data.refcount = 0;
387 : 10641775 : res->data.lockmode = BUFFER_LOCK_UNLOCK;
388 : :
389 : : /* update cache for the next lookup */
390 : 10641775 : PrivateRefCountEntryLast = ReservedRefCountSlot;
391 : :
392 : 10641775 : ReservedRefCountSlot = -1;
393 : :
394 : 21283550 : return res;
395 : 10641775 : }
396 : :
397 : : /*
398 : : * Slow-path for GetPrivateRefCountEntry(). This is big enough to not be worth
399 : : * inlining. This particularly seems to be true if the compiler is capable of
400 : : * auto-vectorizing the code, as that imposes additional stack-alignment
401 : : * requirements etc.
402 : : */
403 : : static pg_noinline PrivateRefCountEntry *
404 : 16052330 : GetPrivateRefCountEntrySlow(Buffer buffer, bool do_move)
405 : : {
406 : 16052330 : PrivateRefCountEntry *res;
407 : 16052330 : int match = -1;
408 : 16052330 : int i;
409 : :
410 : : /*
411 : : * First search for references in the array, that'll be sufficient in the
412 : : * majority of cases.
413 : : */
414 [ + + ]: 144470970 : for (i = 0; i < REFCOUNT_ARRAY_ENTRIES; i++)
415 : : {
416 [ + + ]: 128418640 : if (PrivateRefCountArrayKeys[i] == buffer)
417 : : {
418 : 5385536 : match = i;
419 : : /* see ReservePrivateRefCountEntry() for why we don't return */
420 : 5385536 : }
421 : 128418640 : }
422 : :
423 [ + + ]: 16052330 : if (likely(match != -1))
424 : : {
425 : : /* update cache for the next lookup */
426 : 5385536 : PrivateRefCountEntryLast = match;
427 : :
428 : 5385536 : return &PrivateRefCountArray[match];
429 : : }
430 : :
431 : : /*
432 : : * By here we know that the buffer, if already pinned, isn't residing in
433 : : * the array.
434 : : *
435 : : * Only look up the buffer in the hashtable if we've previously overflowed
436 : : * into it.
437 : : */
438 [ + + ]: 10666794 : if (PrivateRefCountOverflowed == 0)
439 : 10595830 : return NULL;
440 : :
441 : 70964 : res = hash_search(PrivateRefCountHash, &buffer, HASH_FIND, NULL);
442 : :
443 [ + + ]: 70964 : if (res == NULL)
444 : 5408 : return NULL;
445 [ + + ]: 65556 : else if (!do_move)
446 : : {
447 : : /* caller doesn't want us to move the hash entry into the array */
448 : 64209 : return res;
449 : : }
450 : : else
451 : : {
452 : : /* move buffer from hashtable into the free array slot */
453 : 1347 : bool found;
454 : 1347 : PrivateRefCountEntry *free;
455 : :
456 : : /* Ensure there's a free array slot */
457 : 1347 : ReservePrivateRefCountEntry();
458 : :
459 : : /* Use up the reserved slot */
460 [ + - ]: 1347 : Assert(ReservedRefCountSlot != -1);
461 : 1347 : free = &PrivateRefCountArray[ReservedRefCountSlot];
462 [ + - ]: 1347 : Assert(PrivateRefCountArrayKeys[ReservedRefCountSlot] == free->buffer);
463 [ + - ]: 1347 : Assert(free->buffer == InvalidBuffer);
464 : :
465 : : /* and fill it */
466 : 1347 : free->buffer = buffer;
467 : 1347 : free->data = res->data;
468 : 1347 : PrivateRefCountArrayKeys[ReservedRefCountSlot] = buffer;
469 : : /* update cache for the next lookup */
470 : 1347 : PrivateRefCountEntryLast = match;
471 : :
472 : 1347 : ReservedRefCountSlot = -1;
473 : :
474 : :
475 : : /* delete from hashtable */
476 : 1347 : hash_search(PrivateRefCountHash, &buffer, HASH_REMOVE, &found);
477 [ + - ]: 1347 : Assert(found);
478 [ + - ]: 1347 : Assert(PrivateRefCountOverflowed > 0);
479 : 1347 : PrivateRefCountOverflowed--;
480 : :
481 : 1347 : return free;
482 : 1347 : }
483 : 16052330 : }
484 : :
485 : : /*
486 : : * Return the PrivateRefCount entry for the passed buffer.
487 : : *
488 : : * Returns NULL if a buffer doesn't have a refcount entry. Otherwise, if
489 : : * do_move is true, and the entry resides in the hashtable the entry is
490 : : * optimized for frequent access by moving it to the array.
491 : : */
492 : : static inline PrivateRefCountEntry *
493 : 166226020 : GetPrivateRefCountEntry(Buffer buffer, bool do_move)
494 : : {
495 [ + - ]: 166226020 : Assert(BufferIsValid(buffer));
496 [ + - ]: 166226020 : Assert(!BufferIsLocal(buffer));
497 : :
498 : : /*
499 : : * It's very common to look up the same buffer repeatedly. To make that
500 : : * fast, we have a one-entry cache.
501 : : *
502 : : * In contrast to the loop in GetPrivateRefCountEntrySlow(), here it
503 : : * faster to check PrivateRefCountArray[].buffer, as in the case of a hit
504 : : * fewer addresses are computed and fewer cachelines are accessed. Whereas
505 : : * in GetPrivateRefCountEntrySlow()'s case, checking
506 : : * PrivateRefCountArrayKeys saves a lot of memory accesses.
507 : : */
508 [ + + + + ]: 166226020 : if (likely(PrivateRefCountEntryLast != -1) &&
509 : 166223882 : likely(PrivateRefCountArray[PrivateRefCountEntryLast].buffer == buffer))
510 : : {
511 : 150173690 : return &PrivateRefCountArray[PrivateRefCountEntryLast];
512 : : }
513 : :
514 : : /*
515 : : * The code for the cached lookup is small enough to be worth inlining
516 : : * into the caller. In the miss case however, that empirically doesn't
517 : : * seem worth it.
518 : : */
519 : 16052330 : return GetPrivateRefCountEntrySlow(buffer, do_move);
520 : 166226020 : }
521 : :
522 : : /*
523 : : * Returns how many times the passed buffer is pinned by this backend.
524 : : *
525 : : * Only works for shared memory buffers!
526 : : */
527 : : static inline int32
528 : 87161037 : GetPrivateRefCount(Buffer buffer)
529 : : {
530 : 87161037 : PrivateRefCountEntry *ref;
531 : :
532 [ + - ]: 87161037 : Assert(BufferIsValid(buffer));
533 [ + - ]: 87161037 : Assert(!BufferIsLocal(buffer));
534 : :
535 : : /*
536 : : * Not moving the entry - that's ok for the current users, but we might
537 : : * want to change this one day.
538 : : */
539 : 87161037 : ref = GetPrivateRefCountEntry(buffer, false);
540 : :
541 [ + - ]: 87161037 : if (ref == NULL)
542 : 0 : return 0;
543 : 87161037 : return ref->data.refcount;
544 : 87161037 : }
545 : :
546 : : /*
547 : : * Release resources used to track the reference count of a buffer which we no
548 : : * longer have pinned and don't want to pin again immediately.
549 : : */
550 : : static void
551 : 10641775 : ForgetPrivateRefCountEntry(PrivateRefCountEntry *ref)
552 : : {
553 [ + - ]: 10641775 : Assert(ref->data.refcount == 0);
554 [ + - ]: 10641775 : Assert(ref->data.lockmode == BUFFER_LOCK_UNLOCK);
555 : :
556 [ + - + + ]: 10641775 : if (ref >= &PrivateRefCountArray[0] &&
557 : 10641775 : ref < &PrivateRefCountArray[REFCOUNT_ARRAY_ENTRIES])
558 : : {
559 : 10635105 : ref->buffer = InvalidBuffer;
560 : 10635105 : PrivateRefCountArrayKeys[ref - PrivateRefCountArray] = InvalidBuffer;
561 : :
562 : :
563 : : /*
564 : : * Mark the just used entry as reserved - in many scenarios that
565 : : * allows us to avoid ever having to search the array/hash for free
566 : : * entries.
567 : : */
568 : 10635105 : ReservedRefCountSlot = ref - PrivateRefCountArray;
569 : 10635105 : }
570 : : else
571 : : {
572 : 6670 : bool found;
573 : 6670 : Buffer buffer = ref->buffer;
574 : :
575 : 6670 : hash_search(PrivateRefCountHash, &buffer, HASH_REMOVE, &found);
576 [ + - ]: 6670 : Assert(found);
577 [ + - ]: 6670 : Assert(PrivateRefCountOverflowed > 0);
578 : 6670 : PrivateRefCountOverflowed--;
579 : 6670 : }
580 : 10641775 : }
581 : :
582 : : /*
583 : : * BufferIsPinned
584 : : * True iff the buffer is pinned (also checks for valid buffer number).
585 : : *
586 : : * NOTE: what we check here is that *this* backend holds a pin on
587 : : * the buffer. We do not care whether some other backend does.
588 : : */
589 : : #define BufferIsPinned(bufnum) \
590 : : ( \
591 : : !BufferIsValid(bufnum) ? \
592 : : false \
593 : : : \
594 : : BufferIsLocal(bufnum) ? \
595 : : (LocalRefCount[-(bufnum) - 1] > 0) \
596 : : : \
597 : : (GetPrivateRefCount(bufnum) > 0) \
598 : : )
599 : :
600 : :
601 : : static Buffer ReadBuffer_common(Relation rel,
602 : : SMgrRelation smgr, char smgr_persistence,
603 : : ForkNumber forkNum, BlockNumber blockNum,
604 : : ReadBufferMode mode, BufferAccessStrategy strategy);
605 : : static BlockNumber ExtendBufferedRelCommon(BufferManagerRelation bmr,
606 : : ForkNumber fork,
607 : : BufferAccessStrategy strategy,
608 : : uint32 flags,
609 : : uint32 extend_by,
610 : : BlockNumber extend_upto,
611 : : Buffer *buffers,
612 : : uint32 *extended_by);
613 : : static BlockNumber ExtendBufferedRelShared(BufferManagerRelation bmr,
614 : : ForkNumber fork,
615 : : BufferAccessStrategy strategy,
616 : : uint32 flags,
617 : : uint32 extend_by,
618 : : BlockNumber extend_upto,
619 : : Buffer *buffers,
620 : : uint32 *extended_by);
621 : : static bool PinBuffer(BufferDesc *buf, BufferAccessStrategy strategy,
622 : : bool skip_if_not_valid);
623 : : static void PinBuffer_Locked(BufferDesc *buf);
624 : : static void UnpinBuffer(BufferDesc *buf);
625 : : static void UnpinBufferNoOwner(BufferDesc *buf);
626 : : static void BufferSync(int flags);
627 : : static int SyncOneBuffer(int buf_id, bool skip_recently_used,
628 : : WritebackContext *wb_context);
629 : : static void WaitIO(BufferDesc *buf);
630 : : static void AbortBufferIO(Buffer buffer);
631 : : static void shared_buffer_write_error_callback(void *arg);
632 : : static void local_buffer_write_error_callback(void *arg);
633 : : static inline BufferDesc *BufferAlloc(SMgrRelation smgr,
634 : : char relpersistence,
635 : : ForkNumber forkNum,
636 : : BlockNumber blockNum,
637 : : BufferAccessStrategy strategy,
638 : : bool *foundPtr, IOContext io_context);
639 : : static bool AsyncReadBuffers(ReadBuffersOperation *operation, int *nblocks_progress);
640 : : static void CheckReadBuffersOperation(ReadBuffersOperation *operation, bool is_complete);
641 : : static Buffer GetVictimBuffer(BufferAccessStrategy strategy, IOContext io_context);
642 : : static void FlushUnlockedBuffer(BufferDesc *buf, SMgrRelation reln,
643 : : IOObject io_object, IOContext io_context);
644 : : static void FlushBuffer(BufferDesc *buf, SMgrRelation reln,
645 : : IOObject io_object, IOContext io_context);
646 : : static void FindAndDropRelationBuffers(RelFileLocator rlocator,
647 : : ForkNumber forkNum,
648 : : BlockNumber nForkBlock,
649 : : BlockNumber firstDelBlock);
650 : : static void RelationCopyStorageUsingBuffer(RelFileLocator srclocator,
651 : : RelFileLocator dstlocator,
652 : : ForkNumber forkNum, bool permanent);
653 : : static void AtProcExit_Buffers(int code, Datum arg);
654 : : static void CheckForBufferLeaks(void);
655 : : #ifdef USE_ASSERT_CHECKING
656 : : static void AssertNotCatalogBufferLock(Buffer buffer, BufferLockMode mode);
657 : : #endif
658 : : static int rlocator_comparator(const void *p1, const void *p2);
659 : : static inline int buffertag_comparator(const BufferTag *ba, const BufferTag *bb);
660 : : static inline int ckpt_buforder_comparator(const CkptSortItem *a, const CkptSortItem *b);
661 : : static int ts_ckpt_progress_comparator(Datum a, Datum b, void *arg);
662 : :
663 : : static void BufferLockAcquire(Buffer buffer, BufferDesc *buf_hdr, BufferLockMode mode);
664 : : static void BufferLockUnlock(Buffer buffer, BufferDesc *buf_hdr);
665 : : static bool BufferLockConditional(Buffer buffer, BufferDesc *buf_hdr, BufferLockMode mode);
666 : : static bool BufferLockHeldByMeInMode(BufferDesc *buf_hdr, BufferLockMode mode);
667 : : static bool BufferLockHeldByMe(BufferDesc *buf_hdr);
668 : : static inline void BufferLockDisown(Buffer buffer, BufferDesc *buf_hdr);
669 : : static inline int BufferLockDisownInternal(Buffer buffer, BufferDesc *buf_hdr);
670 : : static inline bool BufferLockAttempt(BufferDesc *buf_hdr, BufferLockMode mode);
671 : : static void BufferLockQueueSelf(BufferDesc *buf_hdr, BufferLockMode mode);
672 : : static void BufferLockDequeueSelf(BufferDesc *buf_hdr);
673 : : static void BufferLockWakeup(BufferDesc *buf_hdr, bool unlocked);
674 : : static void BufferLockProcessRelease(BufferDesc *buf_hdr, BufferLockMode mode, uint64 lockstate);
675 : : static inline uint64 BufferLockReleaseSub(BufferLockMode mode);
676 : :
677 : :
678 : : /*
679 : : * Implementation of PrefetchBuffer() for shared buffers.
680 : : */
681 : : PrefetchBufferResult
682 : 3645 : PrefetchSharedBuffer(SMgrRelation smgr_reln,
683 : : ForkNumber forkNum,
684 : : BlockNumber blockNum)
685 : : {
686 : 3645 : PrefetchBufferResult result = {InvalidBuffer, false};
687 : 3645 : BufferTag newTag; /* identity of requested block */
688 : 3645 : uint32 newHash; /* hash value for newTag */
689 : 3645 : LWLock *newPartitionLock; /* buffer partition lock for it */
690 : 3645 : int buf_id;
691 : :
692 [ + - ]: 3645 : Assert(BlockNumberIsValid(blockNum));
693 : :
694 : : /* create a tag so we can lookup the buffer */
695 : 7290 : InitBufferTag(&newTag, &smgr_reln->smgr_rlocator.locator,
696 : 3645 : forkNum, blockNum);
697 : :
698 : : /* determine its hash code and partition lock ID */
699 : 3645 : newHash = BufTableHashCode(&newTag);
700 : 3645 : newPartitionLock = BufMappingPartitionLock(newHash);
701 : :
702 : : /* see if the block is in the buffer pool already */
703 : 3645 : LWLockAcquire(newPartitionLock, LW_SHARED);
704 : 3645 : buf_id = BufTableLookup(&newTag, newHash);
705 : 3645 : LWLockRelease(newPartitionLock);
706 : :
707 : : /* If not in buffers, initiate prefetch */
708 [ + - ]: 3645 : if (buf_id < 0)
709 : : {
710 : : #ifdef USE_PREFETCH
711 : : /*
712 : : * Try to initiate an asynchronous read. This returns false in
713 : : * recovery if the relation file doesn't exist.
714 : : */
715 [ # # # # ]: 0 : if ((io_direct_flags & IO_DIRECT_DATA) == 0 &&
716 : 0 : smgrprefetch(smgr_reln, forkNum, blockNum, 1))
717 : : {
718 : 0 : result.initiated_io = true;
719 : 0 : }
720 : : #endif /* USE_PREFETCH */
721 : 0 : }
722 : : else
723 : : {
724 : : /*
725 : : * Report the buffer it was in at that time. The caller may be able
726 : : * to avoid a buffer table lookup, but it's not pinned and it must be
727 : : * rechecked!
728 : : */
729 : 3645 : result.recent_buffer = buf_id + 1;
730 : : }
731 : :
732 : : /*
733 : : * If the block *is* in buffers, we do nothing. This is not really ideal:
734 : : * the block might be just about to be evicted, which would be stupid
735 : : * since we know we are going to need it soon. But the only easy answer
736 : : * is to bump the usage_count, which does not seem like a great solution:
737 : : * when the caller does ultimately touch the block, usage_count would get
738 : : * bumped again, resulting in too much favoritism for blocks that are
739 : : * involved in a prefetch sequence. A real fix would involve some
740 : : * additional per-buffer state, and it's not clear that there's enough of
741 : : * a problem to justify that.
742 : : */
743 : :
744 : : return result;
745 : 3645 : }
746 : :
747 : : /*
748 : : * PrefetchBuffer -- initiate asynchronous read of a block of a relation
749 : : *
750 : : * This is named by analogy to ReadBuffer but doesn't actually allocate a
751 : : * buffer. Instead it tries to ensure that a future ReadBuffer for the given
752 : : * block will not be delayed by the I/O. Prefetching is optional.
753 : : *
754 : : * There are three possible outcomes:
755 : : *
756 : : * 1. If the block is already cached, the result includes a valid buffer that
757 : : * could be used by the caller to avoid the need for a later buffer lookup, but
758 : : * it's not pinned, so the caller must recheck it.
759 : : *
760 : : * 2. If the kernel has been asked to initiate I/O, the initiated_io member is
761 : : * true. Currently there is no way to know if the data was already cached by
762 : : * the kernel and therefore didn't really initiate I/O, and no way to know when
763 : : * the I/O completes other than using synchronous ReadBuffer().
764 : : *
765 : : * 3. Otherwise, the buffer wasn't already cached by PostgreSQL, and
766 : : * USE_PREFETCH is not defined (this build doesn't support prefetching due to
767 : : * lack of a kernel facility), direct I/O is enabled, or the underlying
768 : : * relation file wasn't found and we are in recovery. (If the relation file
769 : : * wasn't found and we are not in recovery, an error is raised).
770 : : */
771 : : PrefetchBufferResult
772 : 3895 : PrefetchBuffer(Relation reln, ForkNumber forkNum, BlockNumber blockNum)
773 : : {
774 [ + - ]: 3895 : Assert(RelationIsValid(reln));
775 [ + - ]: 3895 : Assert(BlockNumberIsValid(blockNum));
776 : :
777 [ + + ]: 3895 : if (RelationUsesLocalBuffers(reln))
778 : : {
779 : : /* see comments in ReadBufferExtended */
780 [ + - + - ]: 250 : if (RELATION_IS_OTHER_TEMP(reln))
781 [ # # # # ]: 0 : ereport(ERROR,
782 : : (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
783 : : errmsg("cannot access temporary tables of other sessions")));
784 : :
785 : : /* pass it off to localbuf.c */
786 : 250 : return PrefetchLocalBuffer(RelationGetSmgr(reln), forkNum, blockNum);
787 : : }
788 : : else
789 : : {
790 : : /* pass it to the shared buffer version */
791 : 3645 : return PrefetchSharedBuffer(RelationGetSmgr(reln), forkNum, blockNum);
792 : : }
793 : 3895 : }
794 : :
795 : : /*
796 : : * ReadRecentBuffer -- try to pin a block in a recently observed buffer
797 : : *
798 : : * Compared to ReadBuffer(), this avoids a buffer mapping lookup when it's
799 : : * successful. Return true if the buffer is valid and still has the expected
800 : : * tag. In that case, the buffer is pinned and the usage count is bumped.
801 : : */
802 : : bool
803 : 0 : ReadRecentBuffer(RelFileLocator rlocator, ForkNumber forkNum, BlockNumber blockNum,
804 : : Buffer recent_buffer)
805 : : {
806 : 0 : BufferDesc *bufHdr;
807 : 0 : BufferTag tag;
808 : 0 : uint64 buf_state;
809 : :
810 [ # # ]: 0 : Assert(BufferIsValid(recent_buffer));
811 : :
812 : 0 : ResourceOwnerEnlarge(CurrentResourceOwner);
813 : 0 : ReservePrivateRefCountEntry();
814 : 0 : InitBufferTag(&tag, &rlocator, forkNum, blockNum);
815 : :
816 [ # # ]: 0 : if (BufferIsLocal(recent_buffer))
817 : : {
818 : 0 : int b = -recent_buffer - 1;
819 : :
820 : 0 : bufHdr = GetLocalBufferDescriptor(b);
821 : 0 : buf_state = pg_atomic_read_u64(&bufHdr->state);
822 : :
823 : : /* Is it still valid and holding the right tag? */
824 [ # # # # ]: 0 : if ((buf_state & BM_VALID) && BufferTagsEqual(&tag, &bufHdr->tag))
825 : : {
826 : 0 : PinLocalBuffer(bufHdr, true);
827 : :
828 : 0 : pgBufferUsage.local_blks_hit++;
829 : :
830 : 0 : return true;
831 : : }
832 [ # # ]: 0 : }
833 : : else
834 : : {
835 : 0 : bufHdr = GetBufferDescriptor(recent_buffer - 1);
836 : :
837 : : /*
838 : : * Is it still valid and holding the right tag? We do an unlocked tag
839 : : * comparison first, to make it unlikely that we'll increment the
840 : : * usage counter of the wrong buffer, if someone calls us with a very
841 : : * out of date recent_buffer. Then we'll check it again if we get the
842 : : * pin.
843 : : */
844 [ # # # # ]: 0 : if (BufferTagsEqual(&tag, &bufHdr->tag) &&
845 : 0 : PinBuffer(bufHdr, NULL, true))
846 : : {
847 [ # # ]: 0 : if (BufferTagsEqual(&tag, &bufHdr->tag))
848 : : {
849 : 0 : pgBufferUsage.shared_blks_hit++;
850 : 0 : return true;
851 : : }
852 : 0 : UnpinBuffer(bufHdr);
853 : 0 : }
854 : : }
855 : :
856 : 0 : return false;
857 : 0 : }
858 : :
859 : : /*
860 : : * ReadBuffer -- a shorthand for ReadBufferExtended, for reading from main
861 : : * fork with RBM_NORMAL mode and default strategy.
862 : : */
863 : : Buffer
864 : 8891053 : ReadBuffer(Relation reln, BlockNumber blockNum)
865 : : {
866 : 8891053 : return ReadBufferExtended(reln, MAIN_FORKNUM, blockNum, RBM_NORMAL, NULL);
867 : : }
868 : :
869 : : /*
870 : : * ReadBufferExtended -- returns a buffer containing the requested
871 : : * block of the requested relation. If the blknum
872 : : * requested is P_NEW, extend the relation file and
873 : : * allocate a new block. (Caller is responsible for
874 : : * ensuring that only one backend tries to extend a
875 : : * relation at the same time!)
876 : : *
877 : : * Returns: the buffer number for the buffer containing
878 : : * the block read. The returned buffer has been pinned.
879 : : * Does not return on error --- elog's instead.
880 : : *
881 : : * Assume when this function is called, that reln has been opened already.
882 : : *
883 : : * In RBM_NORMAL mode, the page is read from disk, and the page header is
884 : : * validated. An error is thrown if the page header is not valid. (But
885 : : * note that an all-zero page is considered "valid"; see
886 : : * PageIsVerified().)
887 : : *
888 : : * RBM_ZERO_ON_ERROR is like the normal mode, but if the page header is not
889 : : * valid, the page is zeroed instead of throwing an error. This is intended
890 : : * for non-critical data, where the caller is prepared to repair errors.
891 : : *
892 : : * In RBM_ZERO_AND_LOCK mode, if the page isn't in buffer cache already, it's
893 : : * filled with zeros instead of reading it from disk. Useful when the caller
894 : : * is going to fill the page from scratch, since this saves I/O and avoids
895 : : * unnecessary failure if the page-on-disk has corrupt page headers.
896 : : * The page is returned locked to ensure that the caller has a chance to
897 : : * initialize the page before it's made visible to others.
898 : : * Caution: do not use this mode to read a page that is beyond the relation's
899 : : * current physical EOF; that is likely to cause problems in md.c when
900 : : * the page is modified and written out. P_NEW is OK, though.
901 : : *
902 : : * RBM_ZERO_AND_CLEANUP_LOCK is the same as RBM_ZERO_AND_LOCK, but acquires
903 : : * a cleanup-strength lock on the page.
904 : : *
905 : : * RBM_NORMAL_NO_LOG mode is treated the same as RBM_NORMAL here.
906 : : *
907 : : * If strategy is not NULL, a nondefault buffer access strategy is used.
908 : : * See buffer/README for details.
909 : : */
910 : : inline Buffer
911 : 10793784 : ReadBufferExtended(Relation reln, ForkNumber forkNum, BlockNumber blockNum,
912 : : ReadBufferMode mode, BufferAccessStrategy strategy)
913 : : {
914 : 10793784 : Buffer buf;
915 : :
916 : : /*
917 : : * Reject attempts to read non-local temporary relations; we would be
918 : : * likely to get wrong data since we have no visibility into the owning
919 : : * session's local buffers.
920 : : */
921 [ + + + - ]: 10793784 : if (RELATION_IS_OTHER_TEMP(reln))
922 [ # # # # ]: 0 : ereport(ERROR,
923 : : (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
924 : : errmsg("cannot access temporary tables of other sessions")));
925 : :
926 : : /*
927 : : * Read the buffer, and update pgstat counters to reflect a cache hit or
928 : : * miss.
929 : : */
930 : 21587568 : buf = ReadBuffer_common(reln, RelationGetSmgr(reln), 0,
931 : 10793784 : forkNum, blockNum, mode, strategy);
932 : :
933 : 21587568 : return buf;
934 : 10793784 : }
935 : :
936 : :
937 : : /*
938 : : * ReadBufferWithoutRelcache -- like ReadBufferExtended, but doesn't require
939 : : * a relcache entry for the relation.
940 : : *
941 : : * Pass permanent = true for a RELPERSISTENCE_PERMANENT relation, and
942 : : * permanent = false for a RELPERSISTENCE_UNLOGGED relation. This function
943 : : * cannot be used for temporary relations (and making that work might be
944 : : * difficult, unless we only want to read temporary relations for our own
945 : : * ProcNumber).
946 : : */
947 : : Buffer
948 : 2904 : ReadBufferWithoutRelcache(RelFileLocator rlocator, ForkNumber forkNum,
949 : : BlockNumber blockNum, ReadBufferMode mode,
950 : : BufferAccessStrategy strategy, bool permanent)
951 : : {
952 : 2904 : SMgrRelation smgr = smgropen(rlocator, INVALID_PROC_NUMBER);
953 : :
954 : 8712 : return ReadBuffer_common(NULL, smgr,
955 : 2904 : permanent ? RELPERSISTENCE_PERMANENT : RELPERSISTENCE_UNLOGGED,
956 : 2904 : forkNum, blockNum,
957 : 2904 : mode, strategy);
958 : 2904 : }
959 : :
960 : : /*
961 : : * Convenience wrapper around ExtendBufferedRelBy() extending by one block.
962 : : */
963 : : Buffer
964 : 8685 : ExtendBufferedRel(BufferManagerRelation bmr,
965 : : ForkNumber forkNum,
966 : : BufferAccessStrategy strategy,
967 : : uint32 flags)
968 : : {
969 : 8685 : Buffer buf;
970 : 8685 : uint32 extend_by = 1;
971 : :
972 : 8685 : ExtendBufferedRelBy(bmr, forkNum, strategy, flags, extend_by,
973 : : &buf, &extend_by);
974 : :
975 : 17370 : return buf;
976 : 8685 : }
977 : :
978 : : /*
979 : : * Extend relation by multiple blocks.
980 : : *
981 : : * Tries to extend the relation by extend_by blocks. Depending on the
982 : : * availability of resources the relation may end up being extended by a
983 : : * smaller number of pages (unless an error is thrown, always by at least one
984 : : * page). *extended_by is updated to the number of pages the relation has been
985 : : * extended to.
986 : : *
987 : : * buffers needs to be an array that is at least extend_by long. Upon
988 : : * completion, the first extend_by array elements will point to a pinned
989 : : * buffer.
990 : : *
991 : : * If EB_LOCK_FIRST is part of flags, the first returned buffer is
992 : : * locked. This is useful for callers that want a buffer that is guaranteed to
993 : : * be empty.
994 : : */
995 : : BlockNumber
996 : 26696 : ExtendBufferedRelBy(BufferManagerRelation bmr,
997 : : ForkNumber fork,
998 : : BufferAccessStrategy strategy,
999 : : uint32 flags,
1000 : : uint32 extend_by,
1001 : : Buffer *buffers,
1002 : : uint32 *extended_by)
1003 : : {
1004 [ + - ]: 26696 : Assert((bmr.rel != NULL) != (bmr.smgr != NULL));
1005 [ - + # # ]: 26696 : Assert(bmr.smgr == NULL || bmr.relpersistence != '\0');
1006 [ + - ]: 26696 : Assert(extend_by > 0);
1007 : :
1008 [ - + ]: 26696 : if (bmr.relpersistence == '\0')
1009 : 26696 : bmr.relpersistence = bmr.rel->rd_rel->relpersistence;
1010 : :
1011 : 53392 : return ExtendBufferedRelCommon(bmr, fork, strategy, flags,
1012 : 26696 : extend_by, InvalidBlockNumber,
1013 : 26696 : buffers, extended_by);
1014 : : }
1015 : :
1016 : : /*
1017 : : * Extend the relation so it is at least extend_to blocks large, return buffer
1018 : : * (extend_to - 1).
1019 : : *
1020 : : * This is useful for callers that want to write a specific page, regardless
1021 : : * of the current size of the relation (e.g. useful for visibilitymap and for
1022 : : * crash recovery).
1023 : : */
1024 : : Buffer
1025 : 758 : ExtendBufferedRelTo(BufferManagerRelation bmr,
1026 : : ForkNumber fork,
1027 : : BufferAccessStrategy strategy,
1028 : : uint32 flags,
1029 : : BlockNumber extend_to,
1030 : : ReadBufferMode mode)
1031 : : {
1032 : 758 : BlockNumber current_size;
1033 : 758 : uint32 extended_by = 0;
1034 : 758 : Buffer buffer = InvalidBuffer;
1035 : 758 : Buffer buffers[64];
1036 : :
1037 [ + - ]: 758 : Assert((bmr.rel != NULL) != (bmr.smgr != NULL));
1038 [ - + # # ]: 758 : Assert(bmr.smgr == NULL || bmr.relpersistence != '\0');
1039 [ + - ]: 758 : Assert(extend_to != InvalidBlockNumber && extend_to > 0);
1040 : :
1041 [ - + ]: 758 : if (bmr.relpersistence == '\0')
1042 : 758 : bmr.relpersistence = bmr.rel->rd_rel->relpersistence;
1043 : :
1044 : : /*
1045 : : * If desired, create the file if it doesn't exist. If
1046 : : * smgr_cached_nblocks[fork] is positive then it must exist, no need for
1047 : : * an smgrexists call.
1048 : : */
1049 [ - + ]: 758 : if ((flags & EB_CREATE_FORK_IF_NEEDED) &&
1050 [ + - + + ]: 758 : (BMR_GET_SMGR(bmr)->smgr_cached_nblocks[fork] == 0 ||
1051 [ + - + - : 758 : BMR_GET_SMGR(bmr)->smgr_cached_nblocks[fork] == InvalidBlockNumber) &&
- + ]
1052 [ + - ]: 754 : !smgrexists(BMR_GET_SMGR(bmr), fork))
1053 : : {
1054 : 754 : LockRelationForExtension(bmr.rel, ExclusiveLock);
1055 : :
1056 : : /* recheck, fork might have been created concurrently */
1057 [ + - - + ]: 754 : if (!smgrexists(BMR_GET_SMGR(bmr), fork))
1058 [ + - ]: 754 : smgrcreate(BMR_GET_SMGR(bmr), fork, flags & EB_PERFORMING_RECOVERY);
1059 : :
1060 : 754 : UnlockRelationForExtension(bmr.rel, ExclusiveLock);
1061 : 754 : }
1062 : :
1063 : : /*
1064 : : * If requested, invalidate size cache, so that smgrnblocks asks the
1065 : : * kernel.
1066 : : */
1067 [ - + ]: 758 : if (flags & EB_CLEAR_SIZE_CACHE)
1068 [ + - ]: 758 : BMR_GET_SMGR(bmr)->smgr_cached_nblocks[fork] = InvalidBlockNumber;
1069 : :
1070 : : /*
1071 : : * Estimate how many pages we'll need to extend by. This avoids acquiring
1072 : : * unnecessarily many victim buffers.
1073 : : */
1074 [ + - ]: 758 : current_size = smgrnblocks(BMR_GET_SMGR(bmr), fork);
1075 : :
1076 : : /*
1077 : : * Since no-one else can be looking at the page contents yet, there is no
1078 : : * difference between an exclusive lock and a cleanup-strength lock. Note
1079 : : * that we pass the original mode to ReadBuffer_common() below, when
1080 : : * falling back to reading the buffer to a concurrent relation extension.
1081 : : */
1082 [ + - - + ]: 758 : if (mode == RBM_ZERO_AND_LOCK || mode == RBM_ZERO_AND_CLEANUP_LOCK)
1083 : 0 : flags |= EB_LOCK_TARGET;
1084 : :
1085 [ + + ]: 1516 : while (current_size < extend_to)
1086 : : {
1087 : 758 : uint32 num_pages = lengthof(buffers);
1088 : 758 : BlockNumber first_block;
1089 : :
1090 [ - + ]: 758 : if ((uint64) current_size + num_pages > extend_to)
1091 : 758 : num_pages = extend_to - current_size;
1092 : :
1093 : 1516 : first_block = ExtendBufferedRelCommon(bmr, fork, strategy, flags,
1094 : 758 : num_pages, extend_to,
1095 : 758 : buffers, &extended_by);
1096 : :
1097 : 758 : current_size = first_block + extended_by;
1098 [ - + # # ]: 758 : Assert(num_pages != 0 || current_size >= extend_to);
1099 : :
1100 [ + + ]: 2426 : for (uint32 i = 0; i < extended_by; i++)
1101 : : {
1102 [ + + ]: 1668 : if (first_block + i != extend_to - 1)
1103 : 910 : ReleaseBuffer(buffers[i]);
1104 : : else
1105 : 758 : buffer = buffers[i];
1106 : 1668 : }
1107 : 758 : }
1108 : :
1109 : : /*
1110 : : * It's possible that another backend concurrently extended the relation.
1111 : : * In that case read the buffer.
1112 : : *
1113 : : * XXX: Should we control this via a flag?
1114 : : */
1115 [ + - ]: 758 : if (buffer == InvalidBuffer)
1116 : : {
1117 [ # # ]: 0 : Assert(extended_by == 0);
1118 [ # # ]: 0 : buffer = ReadBuffer_common(bmr.rel, BMR_GET_SMGR(bmr), bmr.relpersistence,
1119 : 0 : fork, extend_to - 1, mode, strategy);
1120 : 0 : }
1121 : :
1122 : 1516 : return buffer;
1123 : 758 : }
1124 : :
1125 : : /*
1126 : : * Lock and optionally zero a buffer, as part of the implementation of
1127 : : * RBM_ZERO_AND_LOCK or RBM_ZERO_AND_CLEANUP_LOCK. The buffer must be already
1128 : : * pinned. If the buffer is not already valid, it is zeroed and made valid.
1129 : : */
1130 : : static void
1131 : 3095 : ZeroAndLockBuffer(Buffer buffer, ReadBufferMode mode, bool already_valid)
1132 : : {
1133 : 3095 : BufferDesc *bufHdr;
1134 : 3095 : bool need_to_zero;
1135 : 3095 : bool isLocalBuf = BufferIsLocal(buffer);
1136 : :
1137 [ - + # # ]: 3095 : Assert(mode == RBM_ZERO_AND_LOCK || mode == RBM_ZERO_AND_CLEANUP_LOCK);
1138 : :
1139 [ + + ]: 3095 : if (already_valid)
1140 : : {
1141 : : /*
1142 : : * If the caller already knew the buffer was valid, we can skip some
1143 : : * header interaction. The caller just wants to lock the buffer.
1144 : : */
1145 : 12 : need_to_zero = false;
1146 : 12 : }
1147 [ - + ]: 3083 : else if (isLocalBuf)
1148 : : {
1149 : : /* Simple case for non-shared buffers. */
1150 : 0 : bufHdr = GetLocalBufferDescriptor(-buffer - 1);
1151 : 0 : need_to_zero = StartLocalBufferIO(bufHdr, true, false);
1152 : 0 : }
1153 : : else
1154 : : {
1155 : : /*
1156 : : * Take BM_IO_IN_PROGRESS, or discover that BM_VALID has been set
1157 : : * concurrently. Even though we aren't doing I/O, that ensures that
1158 : : * we don't zero a page that someone else has pinned. An exclusive
1159 : : * content lock wouldn't be enough, because readers are allowed to
1160 : : * drop the content lock after determining that a tuple is visible
1161 : : * (see buffer access rules in README).
1162 : : */
1163 : 3083 : bufHdr = GetBufferDescriptor(buffer - 1);
1164 : 3083 : need_to_zero = StartBufferIO(bufHdr, true, false);
1165 : : }
1166 : :
1167 [ + + ]: 3095 : if (need_to_zero)
1168 : : {
1169 : 3083 : memset(BufferGetPage(buffer), 0, BLCKSZ);
1170 : :
1171 : : /*
1172 : : * Grab the buffer content lock before marking the page as valid, to
1173 : : * make sure that no other backend sees the zeroed page before the
1174 : : * caller has had a chance to initialize it.
1175 : : *
1176 : : * Since no-one else can be looking at the page contents yet, there is
1177 : : * no difference between an exclusive lock and a cleanup-strength
1178 : : * lock. (Note that we cannot use LockBuffer() or
1179 : : * LockBufferForCleanup() here, because they assert that the buffer is
1180 : : * already valid.)
1181 : : */
1182 [ - + ]: 3083 : if (!isLocalBuf)
1183 : 3083 : LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
1184 : :
1185 : : /* Set BM_VALID, terminate IO, and wake up any waiters */
1186 [ - + ]: 3083 : if (isLocalBuf)
1187 : 0 : TerminateLocalBufferIO(bufHdr, false, BM_VALID, false);
1188 : : else
1189 : 3083 : TerminateBufferIO(bufHdr, false, BM_VALID, true, false);
1190 : 3083 : }
1191 [ - + ]: 12 : else if (!isLocalBuf)
1192 : : {
1193 : : /*
1194 : : * The buffer is valid, so we can't zero it. The caller still expects
1195 : : * the page to be locked on return.
1196 : : */
1197 [ + - ]: 12 : if (mode == RBM_ZERO_AND_LOCK)
1198 : 12 : LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
1199 : : else
1200 : 0 : LockBufferForCleanup(buffer);
1201 : 12 : }
1202 : 3095 : }
1203 : :
1204 : : /*
1205 : : * Pin a buffer for a given block. *foundPtr is set to true if the block was
1206 : : * already present, or false if more work is required to either read it in or
1207 : : * zero it.
1208 : : */
1209 : : static pg_attribute_always_inline Buffer
1210 : 11686721 : PinBufferForBlock(Relation rel,
1211 : : SMgrRelation smgr,
1212 : : char persistence,
1213 : : ForkNumber forkNum,
1214 : : BlockNumber blockNum,
1215 : : BufferAccessStrategy strategy,
1216 : : bool *foundPtr)
1217 : : {
1218 : 11686721 : BufferDesc *bufHdr;
1219 : 11686721 : IOContext io_context;
1220 : 11686721 : IOObject io_object;
1221 : :
1222 [ + - ]: 11686721 : Assert(blockNum != P_NEW);
1223 : :
1224 : : /* Persistence should be set before */
1225 [ + + + + : 11686721 : Assert((persistence == RELPERSISTENCE_TEMP ||
+ - ]
1226 : : persistence == RELPERSISTENCE_PERMANENT ||
1227 : : persistence == RELPERSISTENCE_UNLOGGED));
1228 : :
1229 [ + + ]: 11686721 : if (persistence == RELPERSISTENCE_TEMP)
1230 : : {
1231 : 353699 : io_context = IOCONTEXT_NORMAL;
1232 : 353699 : io_object = IOOBJECT_TEMP_RELATION;
1233 : 353699 : }
1234 : : else
1235 : : {
1236 : 11333022 : io_context = IOContextForStrategy(strategy);
1237 : 11333022 : io_object = IOOBJECT_RELATION;
1238 : : }
1239 : :
1240 : 11686721 : TRACE_POSTGRESQL_BUFFER_READ_START(forkNum, blockNum,
1241 : : smgr->smgr_rlocator.locator.spcOid,
1242 : : smgr->smgr_rlocator.locator.dbOid,
1243 : : smgr->smgr_rlocator.locator.relNumber,
1244 : : smgr->smgr_rlocator.backend);
1245 : :
1246 [ + + ]: 11686721 : if (persistence == RELPERSISTENCE_TEMP)
1247 : : {
1248 : 353699 : bufHdr = LocalBufferAlloc(smgr, forkNum, blockNum, foundPtr);
1249 [ + + ]: 353699 : if (*foundPtr)
1250 : 350930 : pgBufferUsage.local_blks_hit++;
1251 : 353699 : }
1252 : : else
1253 : : {
1254 : 22666044 : bufHdr = BufferAlloc(smgr, persistence, forkNum, blockNum,
1255 : 11333022 : strategy, foundPtr, io_context);
1256 [ + + ]: 11333022 : if (*foundPtr)
1257 : 11321557 : pgBufferUsage.shared_blks_hit++;
1258 : : }
1259 [ + + ]: 11686721 : if (rel)
1260 : : {
1261 : : /*
1262 : : * While pgBufferUsage's "read" counter isn't bumped unless we reach
1263 : : * WaitReadBuffers() (so, not for hits, and not for buffers that are
1264 : : * zeroed instead), the per-relation stats always count them.
1265 : : */
1266 [ + + + + : 11680955 : pgstat_count_buffer_read(rel);
+ + ]
1267 [ + + ]: 11680955 : if (*foundPtr)
1268 [ + + + + : 11671495 : pgstat_count_buffer_hit(rel);
- + ]
1269 : 11680955 : }
1270 [ + + ]: 11686721 : if (*foundPtr)
1271 : : {
1272 : 11672487 : pgstat_count_io_op(io_object, io_context, IOOP_HIT, 1, 0);
1273 [ + - ]: 11672487 : if (VacuumCostActive)
1274 : 0 : VacuumCostBalance += VacuumCostPageHit;
1275 : :
1276 : 11672487 : TRACE_POSTGRESQL_BUFFER_READ_DONE(forkNum, blockNum,
1277 : : smgr->smgr_rlocator.locator.spcOid,
1278 : : smgr->smgr_rlocator.locator.dbOid,
1279 : : smgr->smgr_rlocator.locator.relNumber,
1280 : : smgr->smgr_rlocator.backend,
1281 : : true);
1282 : 11672487 : }
1283 : :
1284 : 23373442 : return BufferDescriptorGetBuffer(bufHdr);
1285 : 11686721 : }
1286 : :
1287 : : /*
1288 : : * ReadBuffer_common -- common logic for all ReadBuffer variants
1289 : : *
1290 : : * smgr is required, rel is optional unless using P_NEW.
1291 : : */
1292 : : static pg_attribute_always_inline Buffer
1293 : 10796688 : ReadBuffer_common(Relation rel, SMgrRelation smgr, char smgr_persistence,
1294 : : ForkNumber forkNum,
1295 : : BlockNumber blockNum, ReadBufferMode mode,
1296 : : BufferAccessStrategy strategy)
1297 : : {
1298 : 10796688 : ReadBuffersOperation operation;
1299 : 10796688 : Buffer buffer;
1300 : 10796688 : int flags;
1301 : 10796688 : char persistence;
1302 : :
1303 : : /*
1304 : : * Backward compatibility path, most code should use ExtendBufferedRel()
1305 : : * instead, as acquiring the extension lock inside ExtendBufferedRel()
1306 : : * scales a lot better.
1307 : : */
1308 [ + + ]: 10796688 : if (unlikely(blockNum == P_NEW))
1309 : : {
1310 : 61 : uint32 flags = EB_SKIP_EXTENSION_LOCK;
1311 : :
1312 : : /*
1313 : : * Since no-one else can be looking at the page contents yet, there is
1314 : : * no difference between an exclusive lock and a cleanup-strength
1315 : : * lock.
1316 : : */
1317 [ + - - + ]: 61 : if (mode == RBM_ZERO_AND_LOCK || mode == RBM_ZERO_AND_CLEANUP_LOCK)
1318 : 0 : flags |= EB_LOCK_FIRST;
1319 : :
1320 : 61 : return ExtendBufferedRel(BMR_REL(rel), forkNum, strategy, flags);
1321 : 61 : }
1322 : :
1323 [ + + ]: 10796627 : if (rel)
1324 : 10793723 : persistence = rel->rd_rel->relpersistence;
1325 : : else
1326 : 2904 : persistence = smgr_persistence;
1327 : :
1328 [ - + + + ]: 10796627 : if (unlikely(mode == RBM_ZERO_AND_CLEANUP_LOCK ||
1329 : : mode == RBM_ZERO_AND_LOCK))
1330 : : {
1331 : 3095 : bool found;
1332 : :
1333 : 6190 : buffer = PinBufferForBlock(rel, smgr, persistence,
1334 : 3095 : forkNum, blockNum, strategy, &found);
1335 : 3095 : ZeroAndLockBuffer(buffer, mode, found);
1336 : 3095 : return buffer;
1337 : 3095 : }
1338 : :
1339 : : /*
1340 : : * Signal that we are going to immediately wait. If we're immediately
1341 : : * waiting, there is no benefit in actually executing the IO
1342 : : * asynchronously, it would just add dispatch overhead.
1343 : : */
1344 : 10793532 : flags = READ_BUFFERS_SYNCHRONOUSLY;
1345 [ + + ]: 10793532 : if (mode == RBM_ZERO_ON_ERROR)
1346 : 461197 : flags |= READ_BUFFERS_ZERO_ON_ERROR;
1347 : 10793532 : operation.smgr = smgr;
1348 : 10793532 : operation.rel = rel;
1349 : 10793532 : operation.persistence = persistence;
1350 : 10793532 : operation.forknum = forkNum;
1351 : 10793532 : operation.strategy = strategy;
1352 [ + + ]: 10793532 : if (StartReadBuffer(&operation,
1353 : : &buffer,
1354 : 10793532 : blockNum,
1355 : 10793532 : flags))
1356 : 5966 : WaitReadBuffers(&operation);
1357 : :
1358 : 10793532 : return buffer;
1359 : 10796688 : }
1360 : :
1361 : : static pg_attribute_always_inline bool
1362 : 11679530 : StartReadBuffersImpl(ReadBuffersOperation *operation,
1363 : : Buffer *buffers,
1364 : : BlockNumber blockNum,
1365 : : int *nblocks,
1366 : : int flags,
1367 : : bool allow_forwarding)
1368 : : {
1369 : 11679530 : int actual_nblocks = *nblocks;
1370 : 11679530 : int maxcombine = 0;
1371 : 11679530 : bool did_start_io;
1372 : :
1373 [ + + + - ]: 11679530 : Assert(*nblocks == 1 || allow_forwarding);
1374 [ + - ]: 11679530 : Assert(*nblocks > 0);
1375 [ + - ]: 11679530 : Assert(*nblocks <= MAX_IO_COMBINE_LIMIT);
1376 : :
1377 [ + + + + ]: 23363167 : for (int i = 0; i < actual_nblocks; ++i)
1378 : : {
1379 : 11683637 : bool found;
1380 : :
1381 [ + + + + ]: 11683637 : if (allow_forwarding && buffers[i] != InvalidBuffer)
1382 : : {
1383 : 11 : BufferDesc *bufHdr;
1384 : :
1385 : : /*
1386 : : * This is a buffer that was pinned by an earlier call to
1387 : : * StartReadBuffers(), but couldn't be handled in one operation at
1388 : : * that time. The operation was split, and the caller has passed
1389 : : * an already pinned buffer back to us to handle the rest of the
1390 : : * operation. It must continue at the expected block number.
1391 : : */
1392 [ - + ]: 11 : Assert(BufferGetBlockNumber(buffers[i]) == blockNum + i);
1393 : :
1394 : : /*
1395 : : * It might be an already valid buffer (a hit) that followed the
1396 : : * final contiguous block of an earlier I/O (a miss) marking the
1397 : : * end of it, or a buffer that some other backend has since made
1398 : : * valid by performing the I/O for us, in which case we can handle
1399 : : * it as a hit now. It is safe to check for a BM_VALID flag with
1400 : : * a relaxed load, because we got a fresh view of it while pinning
1401 : : * it in the previous call.
1402 : : *
1403 : : * On the other hand if we don't see BM_VALID yet, it must be an
1404 : : * I/O that was split by the previous call and we need to try to
1405 : : * start a new I/O from this block. We're also racing against any
1406 : : * other backend that might start the I/O or even manage to mark
1407 : : * it BM_VALID after this check, but StartBufferIO() will handle
1408 : : * those cases.
1409 : : */
1410 [ + - ]: 11 : if (BufferIsLocal(buffers[i]))
1411 : 0 : bufHdr = GetLocalBufferDescriptor(-buffers[i] - 1);
1412 : : else
1413 : 11 : bufHdr = GetBufferDescriptor(buffers[i] - 1);
1414 [ - + ]: 11 : Assert(pg_atomic_read_u64(&bufHdr->state) & BM_TAG_VALID);
1415 : 11 : found = pg_atomic_read_u64(&bufHdr->state) & BM_VALID;
1416 : 11 : }
1417 : : else
1418 : : {
1419 : 23367252 : buffers[i] = PinBufferForBlock(operation->rel,
1420 : 11683626 : operation->smgr,
1421 : 11683626 : operation->persistence,
1422 : 11683626 : operation->forknum,
1423 : 11683626 : blockNum + i,
1424 : 11683626 : operation->strategy,
1425 : : &found);
1426 : : }
1427 : :
1428 [ + + ]: 11683637 : if (found)
1429 : : {
1430 : : /*
1431 : : * We have a hit. If it's the first block in the requested range,
1432 : : * we can return it immediately and report that WaitReadBuffers()
1433 : : * does not need to be called. If the initial value of *nblocks
1434 : : * was larger, the caller will have to call again for the rest.
1435 : : */
1436 [ + + ]: 11672486 : if (i == 0)
1437 : : {
1438 : 11672475 : *nblocks = 1;
1439 : :
1440 : : #ifdef USE_ASSERT_CHECKING
1441 : :
1442 : : /*
1443 : : * Initialize enough of ReadBuffersOperation to make
1444 : : * CheckReadBuffersOperation() work. Outside of assertions
1445 : : * that's not necessary when no IO is issued.
1446 : : */
1447 : 11672475 : operation->buffers = buffers;
1448 : 11672475 : operation->blocknum = blockNum;
1449 : 11672475 : operation->nblocks = 1;
1450 : 11672475 : operation->nblocks_done = 1;
1451 : 11672475 : CheckReadBuffersOperation(operation, true);
1452 : : #endif
1453 : 11672475 : return false;
1454 : : }
1455 : :
1456 : : /*
1457 : : * Otherwise we already have an I/O to perform, but this block
1458 : : * can't be included as it is already valid. Split the I/O here.
1459 : : * There may or may not be more blocks requiring I/O after this
1460 : : * one, we haven't checked, but they can't be contiguous with this
1461 : : * one in the way. We'll leave this buffer pinned, forwarding it
1462 : : * to the next call, avoiding the need to unpin it here and re-pin
1463 : : * it in the next call.
1464 : : */
1465 : 11 : actual_nblocks = i;
1466 : 11 : break;
1467 : : }
1468 : : else
1469 : : {
1470 : : /*
1471 : : * Check how many blocks we can cover with the same IO. The smgr
1472 : : * implementation might e.g. be limited due to a segment boundary.
1473 : : */
1474 [ + + + + ]: 11151 : if (i == 0 && actual_nblocks > 1)
1475 : : {
1476 : 1278 : maxcombine = smgrmaxcombine(operation->smgr,
1477 : 639 : operation->forknum,
1478 : 639 : blockNum);
1479 [ + - ]: 639 : if (unlikely(maxcombine < actual_nblocks))
1480 : : {
1481 [ # # # # ]: 0 : elog(DEBUG2, "limiting nblocks at %u from %u to %u",
1482 : : blockNum, actual_nblocks, maxcombine);
1483 : 0 : actual_nblocks = maxcombine;
1484 : 0 : }
1485 : 639 : }
1486 : : }
1487 [ + + ]: 11683637 : }
1488 : 7053 : *nblocks = actual_nblocks;
1489 : :
1490 : : /* Populate information needed for I/O. */
1491 : 7053 : operation->buffers = buffers;
1492 : 7053 : operation->blocknum = blockNum;
1493 : 7053 : operation->flags = flags;
1494 : 7053 : operation->nblocks = actual_nblocks;
1495 : 7053 : operation->nblocks_done = 0;
1496 : 7053 : pgaio_wref_clear(&operation->io_wref);
1497 : :
1498 : : /*
1499 : : * When using AIO, start the IO in the background. If not, issue prefetch
1500 : : * requests if desired by the caller.
1501 : : *
1502 : : * The reason we have a dedicated path for IOMETHOD_SYNC here is to
1503 : : * de-risk the introduction of AIO somewhat. It's a large architectural
1504 : : * change, with lots of chances for unanticipated performance effects.
1505 : : *
1506 : : * Use of IOMETHOD_SYNC already leads to not actually performing IO
1507 : : * asynchronously, but without the check here we'd execute IO earlier than
1508 : : * we used to. Eventually this IOMETHOD_SYNC specific path should go away.
1509 : : */
1510 [ + - ]: 7053 : if (io_method != IOMETHOD_SYNC)
1511 : : {
1512 : : /*
1513 : : * Try to start IO asynchronously. It's possible that no IO needs to
1514 : : * be started, if another backend already performed the IO.
1515 : : *
1516 : : * Note that if an IO is started, it might not cover the entire
1517 : : * requested range, e.g. because an intermediary block has been read
1518 : : * in by another backend. In that case any "trailing" buffers we
1519 : : * already pinned above will be "forwarded" by read_stream.c to the
1520 : : * next call to StartReadBuffers().
1521 : : *
1522 : : * This is signalled to the caller by decrementing *nblocks *and*
1523 : : * reducing operation->nblocks. The latter is done here, but not below
1524 : : * WaitReadBuffers(), as in WaitReadBuffers() we can't "shorten" the
1525 : : * overall read size anymore, we need to retry until done in its
1526 : : * entirety or until failed.
1527 : : */
1528 : 7053 : did_start_io = AsyncReadBuffers(operation, nblocks);
1529 : :
1530 : 7053 : operation->nblocks = *nblocks;
1531 : 7053 : }
1532 : : else
1533 : : {
1534 : 0 : operation->flags |= READ_BUFFERS_SYNCHRONOUSLY;
1535 : :
1536 [ # # ]: 0 : if (flags & READ_BUFFERS_ISSUE_ADVICE)
1537 : : {
1538 : : /*
1539 : : * In theory we should only do this if PinBufferForBlock() had to
1540 : : * allocate new buffers above. That way, if two calls to
1541 : : * StartReadBuffers() were made for the same blocks before
1542 : : * WaitReadBuffers(), only the first would issue the advice.
1543 : : * That'd be a better simulation of true asynchronous I/O, which
1544 : : * would only start the I/O once, but isn't done here for
1545 : : * simplicity.
1546 : : */
1547 : 0 : smgrprefetch(operation->smgr,
1548 : 0 : operation->forknum,
1549 : 0 : blockNum,
1550 : 0 : actual_nblocks);
1551 : 0 : }
1552 : :
1553 : : /*
1554 : : * Indicate that WaitReadBuffers() should be called. WaitReadBuffers()
1555 : : * will initiate the necessary IO.
1556 : : */
1557 : 0 : did_start_io = true;
1558 : : }
1559 : :
1560 : 7053 : CheckReadBuffersOperation(operation, !did_start_io);
1561 : :
1562 : 7053 : return did_start_io;
1563 : 11679530 : }
1564 : :
1565 : : /*
1566 : : * Begin reading a range of blocks beginning at blockNum and extending for
1567 : : * *nblocks. *nblocks and the buffers array are in/out parameters. On entry,
1568 : : * the buffers elements covered by *nblocks must hold either InvalidBuffer or
1569 : : * buffers forwarded by an earlier call to StartReadBuffers() that was split
1570 : : * and is now being continued. On return, *nblocks holds the number of blocks
1571 : : * accepted by this operation. If it is less than the original number then
1572 : : * this operation has been split, but buffer elements up to the original
1573 : : * requested size may hold forwarded buffers to be used for a continuing
1574 : : * operation. The caller must either start a new I/O beginning at the block
1575 : : * immediately following the blocks accepted by this call and pass those
1576 : : * buffers back in, or release them if it chooses not to. It shouldn't make
1577 : : * any other use of or assumptions about forwarded buffers.
1578 : : *
1579 : : * If false is returned, no I/O is necessary and the buffers covered by
1580 : : * *nblocks on exit are valid and ready to be accessed. If true is returned,
1581 : : * an I/O has been started, and WaitReadBuffers() must be called with the same
1582 : : * operation object before the buffers covered by *nblocks on exit can be
1583 : : * accessed. Along with the operation object, the caller-supplied array of
1584 : : * buffers must remain valid until WaitReadBuffers() is called, and any
1585 : : * forwarded buffers must also be preserved for a continuing call unless
1586 : : * they are explicitly released.
1587 : : */
1588 : : bool
1589 : 401903 : StartReadBuffers(ReadBuffersOperation *operation,
1590 : : Buffer *buffers,
1591 : : BlockNumber blockNum,
1592 : : int *nblocks,
1593 : : int flags)
1594 : : {
1595 : 401903 : return StartReadBuffersImpl(operation, buffers, blockNum, nblocks, flags,
1596 : : true /* expect forwarded buffers */ );
1597 : : }
1598 : :
1599 : : /*
1600 : : * Single block version of the StartReadBuffers(). This might save a few
1601 : : * instructions when called from another translation unit, because it is
1602 : : * specialized for nblocks == 1.
1603 : : *
1604 : : * This version does not support "forwarded" buffers: they cannot be created
1605 : : * by reading only one block and *buffer is ignored on entry.
1606 : : */
1607 : : bool
1608 : 11277627 : StartReadBuffer(ReadBuffersOperation *operation,
1609 : : Buffer *buffer,
1610 : : BlockNumber blocknum,
1611 : : int flags)
1612 : : {
1613 : 11277627 : int nblocks = 1;
1614 : 11277627 : bool result;
1615 : :
1616 : 11277627 : result = StartReadBuffersImpl(operation, buffer, blocknum, &nblocks, flags,
1617 : : false /* single block, no forwarding */ );
1618 [ + - ]: 11277627 : Assert(nblocks == 1); /* single block can't be short */
1619 : :
1620 : 22555254 : return result;
1621 : 11277627 : }
1622 : :
1623 : : /*
1624 : : * Perform sanity checks on the ReadBuffersOperation.
1625 : : */
1626 : : static void
1627 : 11693436 : CheckReadBuffersOperation(ReadBuffersOperation *operation, bool is_complete)
1628 : : {
1629 : : #ifdef USE_ASSERT_CHECKING
1630 [ + - ]: 11693436 : Assert(operation->nblocks_done <= operation->nblocks);
1631 [ + + + - ]: 11693436 : Assert(!is_complete || operation->nblocks == operation->nblocks_done);
1632 : :
1633 [ + + ]: 23399164 : for (int i = 0; i < operation->nblocks; i++)
1634 : : {
1635 : 11705728 : Buffer buffer = operation->buffers[i];
1636 [ + + ]: 11705728 : BufferDesc *buf_hdr = BufferIsLocal(buffer) ?
1637 : 359039 : GetLocalBufferDescriptor(-buffer - 1) :
1638 : 11346689 : GetBufferDescriptor(buffer - 1);
1639 : :
1640 [ + - ]: 11705728 : Assert(BufferGetBlockNumber(buffer) == operation->blocknum + i);
1641 [ + - ]: 11705728 : Assert(pg_atomic_read_u64(&buf_hdr->state) & BM_TAG_VALID);
1642 : :
1643 [ + + ]: 11705728 : if (i < operation->nblocks_done)
1644 [ - + ]: 11683527 : Assert(pg_atomic_read_u64(&buf_hdr->state) & BM_VALID);
1645 : 11705728 : }
1646 : : #endif
1647 : 11693436 : }
1648 : :
1649 : : /* helper for ReadBuffersCanStartIO(), to avoid repetition */
1650 : : static inline bool
1651 : 11151 : ReadBuffersCanStartIOOnce(Buffer buffer, bool nowait)
1652 : : {
1653 [ + + ]: 11151 : if (BufferIsLocal(buffer))
1654 : 5538 : return StartLocalBufferIO(GetLocalBufferDescriptor(-buffer - 1),
1655 : 2769 : true, nowait);
1656 : : else
1657 : 8382 : return StartBufferIO(GetBufferDescriptor(buffer - 1), true, nowait);
1658 : 11151 : }
1659 : :
1660 : : /*
1661 : : * Helper for AsyncReadBuffers that tries to get the buffer ready for IO.
1662 : : */
1663 : : static inline bool
1664 : 11151 : ReadBuffersCanStartIO(Buffer buffer, bool nowait)
1665 : : {
1666 : : /*
1667 : : * If this backend currently has staged IO, we need to submit the pending
1668 : : * IO before waiting for the right to issue IO, to avoid the potential for
1669 : : * deadlocks (and, more commonly, unnecessary delays for other backends).
1670 : : */
1671 [ + + + + ]: 11151 : if (!nowait && pgaio_have_staged())
1672 : : {
1673 [ + - ]: 4 : if (ReadBuffersCanStartIOOnce(buffer, true))
1674 : 4 : return true;
1675 : :
1676 : : /*
1677 : : * Unfortunately StartBufferIO() returning false doesn't allow to
1678 : : * distinguish between the buffer already being valid and IO already
1679 : : * being in progress. Since IO already being in progress is quite
1680 : : * rare, this approach seems fine.
1681 : : */
1682 : 0 : pgaio_submit_staged();
1683 : 0 : }
1684 : :
1685 : 11147 : return ReadBuffersCanStartIOOnce(buffer, nowait);
1686 : 11151 : }
1687 : :
1688 : : /*
1689 : : * Helper for WaitReadBuffers() that processes the results of a readv
1690 : : * operation, raising an error if necessary.
1691 : : */
1692 : : static void
1693 : 6954 : ProcessReadBuffersResult(ReadBuffersOperation *operation)
1694 : : {
1695 : 6954 : PgAioReturn *aio_ret = &operation->io_return;
1696 : 6954 : PgAioResultStatus rs = aio_ret->result.status;
1697 : 6954 : int newly_read_blocks = 0;
1698 : :
1699 [ + - ]: 6954 : Assert(pgaio_wref_valid(&operation->io_wref));
1700 [ + - ]: 6954 : Assert(aio_ret->result.status != PGAIO_RS_UNKNOWN);
1701 : :
1702 : : /*
1703 : : * SMGR reports the number of blocks successfully read as the result of
1704 : : * the IO operation. Thus we can simply add that to ->nblocks_done.
1705 : : */
1706 : :
1707 [ - + ]: 6954 : if (likely(rs != PGAIO_RS_ERROR))
1708 : 6954 : newly_read_blocks = aio_ret->result.result;
1709 : :
1710 [ + - - + ]: 6954 : if (rs == PGAIO_RS_ERROR || rs == PGAIO_RS_WARNING)
1711 : 0 : pgaio_result_report(aio_ret->result, &aio_ret->target_data,
1712 : 0 : rs == PGAIO_RS_ERROR ? ERROR : WARNING);
1713 [ + - ]: 6954 : else if (aio_ret->result.status == PGAIO_RS_PARTIAL)
1714 : : {
1715 : : /*
1716 : : * We'll retry, so we just emit a debug message to the server log (or
1717 : : * not even that in prod scenarios).
1718 : : */
1719 : 0 : pgaio_result_report(aio_ret->result, &aio_ret->target_data, DEBUG1);
1720 [ # # # # ]: 0 : elog(DEBUG3, "partial read, will retry");
1721 : 0 : }
1722 : :
1723 [ + - ]: 6954 : Assert(newly_read_blocks > 0);
1724 [ + - ]: 6954 : Assert(newly_read_blocks <= MAX_IO_COMBINE_LIMIT);
1725 : :
1726 : 6954 : operation->nblocks_done += newly_read_blocks;
1727 : :
1728 [ + - ]: 6954 : Assert(operation->nblocks_done <= operation->nblocks);
1729 : 6954 : }
1730 : :
1731 : : void
1732 : 6954 : WaitReadBuffers(ReadBuffersOperation *operation)
1733 : : {
1734 : 6954 : PgAioReturn *aio_ret = &operation->io_return;
1735 : 6954 : IOContext io_context;
1736 : 6954 : IOObject io_object;
1737 : :
1738 [ + + ]: 6954 : if (operation->persistence == RELPERSISTENCE_TEMP)
1739 : : {
1740 : 484 : io_context = IOCONTEXT_NORMAL;
1741 : 484 : io_object = IOOBJECT_TEMP_RELATION;
1742 : 484 : }
1743 : : else
1744 : : {
1745 : 6470 : io_context = IOContextForStrategy(operation->strategy);
1746 : 6470 : io_object = IOOBJECT_RELATION;
1747 : : }
1748 : :
1749 : : /*
1750 : : * If we get here without an IO operation having been issued, the
1751 : : * io_method == IOMETHOD_SYNC path must have been used. Otherwise the
1752 : : * caller should not have called WaitReadBuffers().
1753 : : *
1754 : : * In the case of IOMETHOD_SYNC, we start - as we used to before the
1755 : : * introducing of AIO - the IO in WaitReadBuffers(). This is done as part
1756 : : * of the retry logic below, no extra code is required.
1757 : : *
1758 : : * This path is expected to eventually go away.
1759 : : */
1760 [ - + # # ]: 6954 : if (!pgaio_wref_valid(&operation->io_wref) && io_method != IOMETHOD_SYNC)
1761 [ # # # # ]: 0 : elog(ERROR, "waiting for read operation that didn't read");
1762 : :
1763 : : /*
1764 : : * To handle partial reads, and IOMETHOD_SYNC, we re-issue IO until we're
1765 : : * done. We may need multiple retries, not just because we could get
1766 : : * multiple partial reads, but also because some of the remaining
1767 : : * to-be-read buffers may have been read in by other backends, limiting
1768 : : * the IO size.
1769 : : */
1770 : 6954 : while (true)
1771 : : {
1772 : 6954 : int ignored_nblocks_progress;
1773 : :
1774 : 6954 : CheckReadBuffersOperation(operation, false);
1775 : :
1776 : : /*
1777 : : * If there is an IO associated with the operation, we may need to
1778 : : * wait for it.
1779 : : */
1780 [ - + ]: 6954 : if (pgaio_wref_valid(&operation->io_wref))
1781 : : {
1782 : : /*
1783 : : * Track the time spent waiting for the IO to complete. As
1784 : : * tracking a wait even if we don't actually need to wait
1785 : : *
1786 : : * a) is not cheap, due to the timestamping overhead
1787 : : *
1788 : : * b) reports some time as waiting, even if we never waited
1789 : : *
1790 : : * we first check if we already know the IO is complete.
1791 : : */
1792 [ + + + + ]: 6954 : if (aio_ret->result.status == PGAIO_RS_UNKNOWN &&
1793 : 658 : !pgaio_wref_check_done(&operation->io_wref))
1794 : : {
1795 : 593 : instr_time io_start = pgstat_prepare_io_time(track_io_timing);
1796 : :
1797 : 593 : pgaio_wref_wait(&operation->io_wref);
1798 : :
1799 : : /*
1800 : : * The IO operation itself was already counted earlier, in
1801 : : * AsyncReadBuffers(), this just accounts for the wait time.
1802 : : */
1803 : 593 : pgstat_count_io_op_time(io_object, io_context, IOOP_READ,
1804 : : io_start, 0, 0);
1805 : 593 : }
1806 : : else
1807 : : {
1808 [ - + ]: 6361 : Assert(pgaio_wref_check_done(&operation->io_wref));
1809 : : }
1810 : :
1811 : : /*
1812 : : * We now are sure the IO completed. Check the results. This
1813 : : * includes reporting on errors if there were any.
1814 : : */
1815 : 6954 : ProcessReadBuffersResult(operation);
1816 : 6954 : }
1817 : :
1818 : : /*
1819 : : * Most of the time, the one IO we already started, will read in
1820 : : * everything. But we need to deal with partial reads and buffers not
1821 : : * needing IO anymore.
1822 : : */
1823 [ + - ]: 6954 : if (operation->nblocks_done == operation->nblocks)
1824 : 6954 : break;
1825 : :
1826 [ # # ]: 0 : CHECK_FOR_INTERRUPTS();
1827 : :
1828 : : /*
1829 : : * This may only complete the IO partially, either because some
1830 : : * buffers were already valid, or because of a partial read.
1831 : : *
1832 : : * NB: In contrast to after the AsyncReadBuffers() call in
1833 : : * StartReadBuffers(), we do *not* reduce
1834 : : * ReadBuffersOperation->nblocks here, callers expect the full
1835 : : * operation to be completed at this point (as more operations may
1836 : : * have been queued).
1837 : : */
1838 : 0 : AsyncReadBuffers(operation, &ignored_nblocks_progress);
1839 [ - - + ]: 6954 : }
1840 : :
1841 : 6954 : CheckReadBuffersOperation(operation, true);
1842 : :
1843 : : /* NB: READ_DONE tracepoint was already executed in completion callback */
1844 : 6954 : }
1845 : :
1846 : : /*
1847 : : * Initiate IO for the ReadBuffersOperation
1848 : : *
1849 : : * This function only starts a single IO at a time. The size of the IO may be
1850 : : * limited to below the to-be-read blocks, if one of the buffers has
1851 : : * concurrently been read in. If the first to-be-read buffer is already valid,
1852 : : * no IO will be issued.
1853 : : *
1854 : : * To support retries after partial reads, the first operation->nblocks_done
1855 : : * buffers are skipped.
1856 : : *
1857 : : * On return *nblocks_progress is updated to reflect the number of buffers
1858 : : * affected by the call. If the first buffer is valid, *nblocks_progress is
1859 : : * set to 1 and operation->nblocks_done is incremented.
1860 : : *
1861 : : * Returns true if IO was initiated, false if no IO was necessary.
1862 : : */
1863 : : static bool
1864 : 7053 : AsyncReadBuffers(ReadBuffersOperation *operation, int *nblocks_progress)
1865 : : {
1866 : 7053 : Buffer *buffers = &operation->buffers[0];
1867 : 7053 : int flags = operation->flags;
1868 : 7053 : BlockNumber blocknum = operation->blocknum;
1869 : 7053 : ForkNumber forknum = operation->forknum;
1870 : 7053 : char persistence = operation->persistence;
1871 : 7053 : int16 nblocks_done = operation->nblocks_done;
1872 : 7053 : Buffer *io_buffers = &operation->buffers[nblocks_done];
1873 : 7053 : int io_buffers_len = 0;
1874 : 7053 : PgAioHandle *ioh;
1875 : 7053 : uint32 ioh_flags = 0;
1876 : 7053 : void *io_pages[MAX_IO_COMBINE_LIMIT];
1877 : 7053 : IOContext io_context;
1878 : 7053 : IOObject io_object;
1879 : 7053 : bool did_start_io;
1880 : :
1881 : : /*
1882 : : * When this IO is executed synchronously, either because the caller will
1883 : : * immediately block waiting for the IO or because IOMETHOD_SYNC is used,
1884 : : * the AIO subsystem needs to know.
1885 : : */
1886 [ + + ]: 7053 : if (flags & READ_BUFFERS_SYNCHRONOUSLY)
1887 : 5967 : ioh_flags |= PGAIO_HF_SYNCHRONOUS;
1888 : :
1889 [ + + ]: 7053 : if (persistence == RELPERSISTENCE_TEMP)
1890 : : {
1891 : 582 : io_context = IOCONTEXT_NORMAL;
1892 : 582 : io_object = IOOBJECT_TEMP_RELATION;
1893 : 582 : ioh_flags |= PGAIO_HF_REFERENCES_LOCAL;
1894 : 582 : }
1895 : : else
1896 : : {
1897 : 6471 : io_context = IOContextForStrategy(operation->strategy);
1898 : 6471 : io_object = IOOBJECT_RELATION;
1899 : : }
1900 : :
1901 : : /*
1902 : : * If zero_damaged_pages is enabled, add the READ_BUFFERS_ZERO_ON_ERROR
1903 : : * flag. The reason for that is that, hopefully, zero_damaged_pages isn't
1904 : : * set globally, but on a per-session basis. The completion callback,
1905 : : * which may be run in other processes, e.g. in IO workers, may have a
1906 : : * different value of the zero_damaged_pages GUC.
1907 : : *
1908 : : * XXX: We probably should eventually use a different flag for
1909 : : * zero_damaged_pages, so we can report different log levels / error codes
1910 : : * for zero_damaged_pages and ZERO_ON_ERROR.
1911 : : */
1912 [ + - ]: 7053 : if (zero_damaged_pages)
1913 : 0 : flags |= READ_BUFFERS_ZERO_ON_ERROR;
1914 : :
1915 : : /*
1916 : : * For the same reason as with zero_damaged_pages we need to use this
1917 : : * backend's ignore_checksum_failure value.
1918 : : */
1919 [ + - ]: 7053 : if (ignore_checksum_failure)
1920 : 0 : flags |= READ_BUFFERS_IGNORE_CHECKSUM_FAILURES;
1921 : :
1922 : :
1923 : : /*
1924 : : * To be allowed to report stats in the local completion callback we need
1925 : : * to prepare to report stats now. This ensures we can safely report the
1926 : : * checksum failure even in a critical section.
1927 : : */
1928 : 7053 : pgstat_prepare_report_checksum_failure(operation->smgr->smgr_rlocator.locator.dbOid);
1929 : :
1930 : : /*
1931 : : * Get IO handle before ReadBuffersCanStartIO(), as pgaio_io_acquire()
1932 : : * might block, which we don't want after setting IO_IN_PROGRESS.
1933 : : *
1934 : : * If we need to wait for IO before we can get a handle, submit
1935 : : * already-staged IO first, so that other backends don't need to wait.
1936 : : * There wouldn't be a deadlock risk, as pgaio_io_acquire() just needs to
1937 : : * wait for already submitted IO, which doesn't require additional locks,
1938 : : * but it could still cause undesirable waits.
1939 : : *
1940 : : * A secondary benefit is that this would allow us to measure the time in
1941 : : * pgaio_io_acquire() without causing undue timer overhead in the common,
1942 : : * non-blocking, case. However, currently the pgstats infrastructure
1943 : : * doesn't really allow that, as it a) asserts that an operation can't
1944 : : * have time without operations b) doesn't have an API to report
1945 : : * "accumulated" time.
1946 : : */
1947 : 7053 : ioh = pgaio_io_acquire_nb(CurrentResourceOwner, &operation->io_return);
1948 [ + - ]: 7053 : if (unlikely(!ioh))
1949 : : {
1950 : 0 : pgaio_submit_staged();
1951 : :
1952 : 0 : ioh = pgaio_io_acquire(CurrentResourceOwner, &operation->io_return);
1953 : 0 : }
1954 : :
1955 : : /*
1956 : : * Check if we can start IO on the first to-be-read buffer.
1957 : : *
1958 : : * If an I/O is already in progress in another backend, we want to wait
1959 : : * for the outcome: either done, or something went wrong and we will
1960 : : * retry.
1961 : : */
1962 [ + + ]: 7053 : if (!ReadBuffersCanStartIO(buffers[nblocks_done], false))
1963 : : {
1964 : : /*
1965 : : * Someone else has already completed this block, we're done.
1966 : : *
1967 : : * When IO is necessary, ->nblocks_done is updated in
1968 : : * ProcessReadBuffersResult(), but that is not called if no IO is
1969 : : * necessary. Thus update here.
1970 : : */
1971 : 1 : operation->nblocks_done += 1;
1972 : 1 : *nblocks_progress = 1;
1973 : :
1974 : 1 : pgaio_io_release(ioh);
1975 : 1 : pgaio_wref_clear(&operation->io_wref);
1976 : 1 : did_start_io = false;
1977 : :
1978 : : /*
1979 : : * Report and track this as a 'hit' for this backend, even though it
1980 : : * must have started out as a miss in PinBufferForBlock(). The other
1981 : : * backend will track this as a 'read'.
1982 : : */
1983 : 1 : TRACE_POSTGRESQL_BUFFER_READ_DONE(forknum, blocknum + operation->nblocks_done,
1984 : : operation->smgr->smgr_rlocator.locator.spcOid,
1985 : : operation->smgr->smgr_rlocator.locator.dbOid,
1986 : : operation->smgr->smgr_rlocator.locator.relNumber,
1987 : : operation->smgr->smgr_rlocator.backend,
1988 : : true);
1989 : :
1990 [ - + ]: 1 : if (persistence == RELPERSISTENCE_TEMP)
1991 : 0 : pgBufferUsage.local_blks_hit += 1;
1992 : : else
1993 : 1 : pgBufferUsage.shared_blks_hit += 1;
1994 : :
1995 [ - + ]: 1 : if (operation->rel)
1996 [ + - + - : 1 : pgstat_count_buffer_hit(operation->rel);
# # ]
1997 : :
1998 : 1 : pgstat_count_io_op(io_object, io_context, IOOP_HIT, 1, 0);
1999 : :
2000 [ + - ]: 1 : if (VacuumCostActive)
2001 : 0 : VacuumCostBalance += VacuumCostPageHit;
2002 : 1 : }
2003 : : else
2004 : : {
2005 : 7052 : instr_time io_start;
2006 : :
2007 : : /* We found a buffer that we need to read in. */
2008 [ + - ]: 7052 : Assert(io_buffers[0] == buffers[nblocks_done]);
2009 : 7052 : io_pages[0] = BufferGetBlock(buffers[nblocks_done]);
2010 : 7052 : io_buffers_len = 1;
2011 : :
2012 : : /*
2013 : : * How many neighboring-on-disk blocks can we scatter-read into other
2014 : : * buffers at the same time? In this case we don't wait if we see an
2015 : : * I/O already in progress. We already set BM_IO_IN_PROGRESS for the
2016 : : * head block, so we should get on with that I/O as soon as possible.
2017 : : */
2018 [ + + ]: 11150 : for (int i = nblocks_done + 1; i < operation->nblocks; i++)
2019 : : {
2020 [ - + ]: 4098 : if (!ReadBuffersCanStartIO(buffers[i], true))
2021 : 0 : break;
2022 : : /* Must be consecutive block numbers. */
2023 [ + - ]: 4098 : Assert(BufferGetBlockNumber(buffers[i - 1]) ==
2024 : : BufferGetBlockNumber(buffers[i]) - 1);
2025 [ + - ]: 4098 : Assert(io_buffers[io_buffers_len] == buffers[i]);
2026 : :
2027 : 4098 : io_pages[io_buffers_len++] = BufferGetBlock(buffers[i]);
2028 : 4098 : }
2029 : :
2030 : : /* get a reference to wait for in WaitReadBuffers() */
2031 : 7052 : pgaio_io_get_wref(ioh, &operation->io_wref);
2032 : :
2033 : : /* provide the list of buffers to the completion callbacks */
2034 : 7052 : pgaio_io_set_handle_data_32(ioh, (uint32 *) io_buffers, io_buffers_len);
2035 : :
2036 : 14104 : pgaio_io_register_callbacks(ioh,
2037 : 7052 : persistence == RELPERSISTENCE_TEMP ?
2038 : : PGAIO_HCB_LOCAL_BUFFER_READV :
2039 : : PGAIO_HCB_SHARED_BUFFER_READV,
2040 : 7052 : flags);
2041 : :
2042 : 7052 : pgaio_io_set_flag(ioh, ioh_flags);
2043 : :
2044 : : /* ---
2045 : : * Even though we're trying to issue IO asynchronously, track the time
2046 : : * in smgrstartreadv():
2047 : : * - if io_method == IOMETHOD_SYNC, we will always perform the IO
2048 : : * immediately
2049 : : * - the io method might not support the IO (e.g. worker IO for a temp
2050 : : * table)
2051 : : * ---
2052 : : */
2053 : 7052 : io_start = pgstat_prepare_io_time(track_io_timing);
2054 : 14104 : smgrstartreadv(ioh, operation->smgr, forknum,
2055 : 7052 : blocknum + nblocks_done,
2056 : 7052 : io_pages, io_buffers_len);
2057 : 14104 : pgstat_count_io_op_time(io_object, io_context, IOOP_READ,
2058 : 7052 : io_start, 1, io_buffers_len * BLCKSZ);
2059 : :
2060 [ + + ]: 7052 : if (persistence == RELPERSISTENCE_TEMP)
2061 : 582 : pgBufferUsage.local_blks_read += io_buffers_len;
2062 : : else
2063 : 6470 : pgBufferUsage.shared_blks_read += io_buffers_len;
2064 : :
2065 : : /*
2066 : : * Track vacuum cost when issuing IO, not after waiting for it.
2067 : : * Otherwise we could end up issuing a lot of IO in a short timespan,
2068 : : * despite a low cost limit.
2069 : : */
2070 [ + - ]: 7052 : if (VacuumCostActive)
2071 : 0 : VacuumCostBalance += VacuumCostPageMiss * io_buffers_len;
2072 : :
2073 : 7052 : *nblocks_progress = io_buffers_len;
2074 : 7052 : did_start_io = true;
2075 : 7052 : }
2076 : :
2077 : 14106 : return did_start_io;
2078 : 7053 : }
2079 : :
2080 : : /*
2081 : : * BufferAlloc -- subroutine for PinBufferForBlock. Handles lookup of a shared
2082 : : * buffer. If no buffer exists already, selects a replacement victim and
2083 : : * evicts the old page, but does NOT read in new page.
2084 : : *
2085 : : * "strategy" can be a buffer replacement strategy object, or NULL for
2086 : : * the default strategy. The selected buffer's usage_count is advanced when
2087 : : * using the default strategy, but otherwise possibly not (see PinBuffer).
2088 : : *
2089 : : * The returned buffer is pinned and is already marked as holding the
2090 : : * desired page. If it already did have the desired page, *foundPtr is
2091 : : * set true. Otherwise, *foundPtr is set false.
2092 : : *
2093 : : * io_context is passed as an output parameter to avoid calling
2094 : : * IOContextForStrategy() when there is a shared buffers hit and no IO
2095 : : * statistics need be captured.
2096 : : *
2097 : : * No locks are held either at entry or exit.
2098 : : */
2099 : : static pg_attribute_always_inline BufferDesc *
2100 : 11333022 : BufferAlloc(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
2101 : : BlockNumber blockNum,
2102 : : BufferAccessStrategy strategy,
2103 : : bool *foundPtr, IOContext io_context)
2104 : : {
2105 : 11333022 : BufferTag newTag; /* identity of requested block */
2106 : 11333022 : uint32 newHash; /* hash value for newTag */
2107 : 11333022 : LWLock *newPartitionLock; /* buffer partition lock for it */
2108 : 11333022 : int existing_buf_id;
2109 : 11333022 : Buffer victim_buffer;
2110 : 11333022 : BufferDesc *victim_buf_hdr;
2111 : 11333022 : uint64 victim_buf_state;
2112 : 11333022 : uint64 set_bits = 0;
2113 : :
2114 : : /* Make sure we will have room to remember the buffer pin */
2115 : 11333022 : ResourceOwnerEnlarge(CurrentResourceOwner);
2116 : 11333022 : ReservePrivateRefCountEntry();
2117 : :
2118 : : /* create a tag so we can lookup the buffer */
2119 : 11333022 : InitBufferTag(&newTag, &smgr->smgr_rlocator.locator, forkNum, blockNum);
2120 : :
2121 : : /* determine its hash code and partition lock ID */
2122 : 11333022 : newHash = BufTableHashCode(&newTag);
2123 : 11333022 : newPartitionLock = BufMappingPartitionLock(newHash);
2124 : :
2125 : : /* see if the block is in the buffer pool already */
2126 : 11333022 : LWLockAcquire(newPartitionLock, LW_SHARED);
2127 : 11333022 : existing_buf_id = BufTableLookup(&newTag, newHash);
2128 [ + + ]: 11333022 : if (existing_buf_id >= 0)
2129 : : {
2130 : 11321558 : BufferDesc *buf;
2131 : 11321558 : bool valid;
2132 : :
2133 : : /*
2134 : : * Found it. Now, pin the buffer so no one can steal it from the
2135 : : * buffer pool, and check to see if the correct data has been loaded
2136 : : * into the buffer.
2137 : : */
2138 : 11321558 : buf = GetBufferDescriptor(existing_buf_id);
2139 : :
2140 : 11321558 : valid = PinBuffer(buf, strategy, false);
2141 : :
2142 : : /* Can release the mapping lock as soon as we've pinned it */
2143 : 11321558 : LWLockRelease(newPartitionLock);
2144 : :
2145 : 11321558 : *foundPtr = true;
2146 : :
2147 [ + + ]: 11321558 : if (!valid)
2148 : : {
2149 : : /*
2150 : : * We can only get here if (a) someone else is still reading in
2151 : : * the page, (b) a previous read attempt failed, or (c) someone
2152 : : * called StartReadBuffers() but not yet WaitReadBuffers().
2153 : : */
2154 : 1 : *foundPtr = false;
2155 : 1 : }
2156 : :
2157 : 11321558 : return buf;
2158 : 11321558 : }
2159 : :
2160 : : /*
2161 : : * Didn't find it in the buffer pool. We'll have to initialize a new
2162 : : * buffer. Remember to unlock the mapping lock while doing the work.
2163 : : */
2164 : 11464 : LWLockRelease(newPartitionLock);
2165 : :
2166 : : /*
2167 : : * Acquire a victim buffer. Somebody else might try to do the same, we
2168 : : * don't hold any conflicting locks. If so we'll have to undo our work
2169 : : * later.
2170 : : */
2171 : 11464 : victim_buffer = GetVictimBuffer(strategy, io_context);
2172 : 11464 : victim_buf_hdr = GetBufferDescriptor(victim_buffer - 1);
2173 : :
2174 : : /*
2175 : : * Try to make a hashtable entry for the buffer under its new tag. If
2176 : : * somebody else inserted another buffer for the tag, we'll release the
2177 : : * victim buffer we acquired and use the already inserted one.
2178 : : */
2179 : 11464 : LWLockAcquire(newPartitionLock, LW_EXCLUSIVE);
2180 : 11464 : existing_buf_id = BufTableInsert(&newTag, newHash, victim_buf_hdr->buf_id);
2181 [ - + ]: 11464 : if (existing_buf_id >= 0)
2182 : : {
2183 : 0 : BufferDesc *existing_buf_hdr;
2184 : 0 : bool valid;
2185 : :
2186 : : /*
2187 : : * Got a collision. Someone has already done what we were about to do.
2188 : : * We'll just handle this as if it were found in the buffer pool in
2189 : : * the first place. First, give up the buffer we were planning to
2190 : : * use.
2191 : : *
2192 : : * We could do this after releasing the partition lock, but then we'd
2193 : : * have to call ResourceOwnerEnlarge() & ReservePrivateRefCountEntry()
2194 : : * before acquiring the lock, for the rare case of such a collision.
2195 : : */
2196 : 0 : UnpinBuffer(victim_buf_hdr);
2197 : :
2198 : : /* remaining code should match code at top of routine */
2199 : :
2200 : 0 : existing_buf_hdr = GetBufferDescriptor(existing_buf_id);
2201 : :
2202 : 0 : valid = PinBuffer(existing_buf_hdr, strategy, false);
2203 : :
2204 : : /* Can release the mapping lock as soon as we've pinned it */
2205 : 0 : LWLockRelease(newPartitionLock);
2206 : :
2207 : 0 : *foundPtr = true;
2208 : :
2209 [ # # ]: 0 : if (!valid)
2210 : : {
2211 : : /*
2212 : : * We can only get here if (a) someone else is still reading in
2213 : : * the page, (b) a previous read attempt failed, or (c) someone
2214 : : * called StartReadBuffers() but not yet WaitReadBuffers().
2215 : : */
2216 : 0 : *foundPtr = false;
2217 : 0 : }
2218 : :
2219 : 0 : return existing_buf_hdr;
2220 : 0 : }
2221 : :
2222 : : /*
2223 : : * Need to lock the buffer header too in order to change its tag.
2224 : : */
2225 : 11464 : victim_buf_state = LockBufHdr(victim_buf_hdr);
2226 : :
2227 : : /* some sanity checks while we hold the buffer header lock */
2228 [ + - ]: 11464 : Assert(BUF_STATE_GET_REFCOUNT(victim_buf_state) == 1);
2229 [ + - ]: 11464 : Assert(!(victim_buf_state & (BM_TAG_VALID | BM_VALID | BM_DIRTY | BM_IO_IN_PROGRESS)));
2230 : :
2231 : 11464 : victim_buf_hdr->tag = newTag;
2232 : :
2233 : : /*
2234 : : * Make sure BM_PERMANENT is set for buffers that must be written at every
2235 : : * checkpoint. Unlogged buffers only need to be written at shutdown
2236 : : * checkpoints, except for their "init" forks, which need to be treated
2237 : : * just like permanent relations.
2238 : : */
2239 : 11464 : set_bits |= BM_TAG_VALID | BUF_USAGECOUNT_ONE;
2240 [ + + - + ]: 11464 : if (relpersistence == RELPERSISTENCE_PERMANENT || forkNum == INIT_FORKNUM)
2241 : 11463 : set_bits |= BM_PERMANENT;
2242 : :
2243 : 22928 : UnlockBufHdrExt(victim_buf_hdr, victim_buf_state,
2244 : 11464 : set_bits, 0, 0);
2245 : :
2246 : 11464 : LWLockRelease(newPartitionLock);
2247 : :
2248 : : /*
2249 : : * Buffer contents are currently invalid.
2250 : : */
2251 : 11464 : *foundPtr = false;
2252 : :
2253 : 11464 : return victim_buf_hdr;
2254 : 11333022 : }
2255 : :
2256 : : /*
2257 : : * InvalidateBuffer -- mark a shared buffer invalid.
2258 : : *
2259 : : * The buffer header spinlock must be held at entry. We drop it before
2260 : : * returning. (This is sane because the caller must have locked the
2261 : : * buffer in order to be sure it should be dropped.)
2262 : : *
2263 : : * This is used only in contexts such as dropping a relation. We assume
2264 : : * that no other backend could possibly be interested in using the page,
2265 : : * so the only reason the buffer might be pinned is if someone else is
2266 : : * trying to write it out. We have to let them finish before we can
2267 : : * reclaim the buffer.
2268 : : *
2269 : : * The buffer could get reclaimed by someone else while we are waiting
2270 : : * to acquire the necessary locks; if so, don't mess it up.
2271 : : */
2272 : : static void
2273 : 19008 : InvalidateBuffer(BufferDesc *buf)
2274 : : {
2275 : 19008 : BufferTag oldTag;
2276 : 19008 : uint32 oldHash; /* hash value for oldTag */
2277 : 19008 : LWLock *oldPartitionLock; /* buffer partition lock for it */
2278 : 19008 : uint32 oldFlags;
2279 : 19008 : uint64 buf_state;
2280 : :
2281 : : /* Save the original buffer tag before dropping the spinlock */
2282 : 19008 : oldTag = buf->tag;
2283 : :
2284 : 19008 : UnlockBufHdr(buf);
2285 : :
2286 : : /*
2287 : : * Need to compute the old tag's hashcode and partition lock ID. XXX is it
2288 : : * worth storing the hashcode in BufferDesc so we need not recompute it
2289 : : * here? Probably not.
2290 : : */
2291 : 19008 : oldHash = BufTableHashCode(&oldTag);
2292 : 19008 : oldPartitionLock = BufMappingPartitionLock(oldHash);
2293 : :
2294 : : retry:
2295 : :
2296 : : /*
2297 : : * Acquire exclusive mapping lock in preparation for changing the buffer's
2298 : : * association.
2299 : : */
2300 : 19008 : LWLockAcquire(oldPartitionLock, LW_EXCLUSIVE);
2301 : :
2302 : : /* Re-lock the buffer header */
2303 : 19008 : buf_state = LockBufHdr(buf);
2304 : :
2305 : : /* If it's changed while we were waiting for lock, do nothing */
2306 [ + - ]: 19008 : if (!BufferTagsEqual(&buf->tag, &oldTag))
2307 : : {
2308 : 0 : UnlockBufHdr(buf);
2309 : 0 : LWLockRelease(oldPartitionLock);
2310 : 0 : return;
2311 : : }
2312 : :
2313 : : /*
2314 : : * We assume the reason for it to be pinned is that either we were
2315 : : * asynchronously reading the page in before erroring out or someone else
2316 : : * is flushing the page out. Wait for the IO to finish. (This could be
2317 : : * an infinite loop if the refcount is messed up... it would be nice to
2318 : : * time out after awhile, but there seems no way to be sure how many loops
2319 : : * may be needed. Note that if the other guy has pinned the buffer but
2320 : : * not yet done StartBufferIO, WaitIO will fall through and we'll
2321 : : * effectively be busy-looping here.)
2322 : : */
2323 [ - + ]: 19008 : if (BUF_STATE_GET_REFCOUNT(buf_state) != 0)
2324 : : {
2325 : 0 : UnlockBufHdr(buf);
2326 : 0 : LWLockRelease(oldPartitionLock);
2327 : : /* safety check: should definitely not be our *own* pin */
2328 [ # # ]: 0 : if (GetPrivateRefCount(BufferDescriptorGetBuffer(buf)) > 0)
2329 [ # # # # ]: 0 : elog(ERROR, "buffer is pinned in InvalidateBuffer");
2330 : 0 : WaitIO(buf);
2331 : 0 : goto retry;
2332 : : }
2333 : :
2334 : : /*
2335 : : * An invalidated buffer should not have any backends waiting to lock the
2336 : : * buffer, therefore BM_LOCK_WAKE_IN_PROGRESS should not be set.
2337 : : */
2338 [ + - ]: 19008 : Assert(!(buf_state & BM_LOCK_WAKE_IN_PROGRESS));
2339 : :
2340 : : /*
2341 : : * Clear out the buffer's tag and flags. We must do this to ensure that
2342 : : * linear scans of the buffer array don't think the buffer is valid.
2343 : : */
2344 : 19008 : oldFlags = buf_state & BUF_FLAG_MASK;
2345 : 19008 : ClearBufferTag(&buf->tag);
2346 : :
2347 : 19008 : UnlockBufHdrExt(buf, buf_state,
2348 : : 0,
2349 : : BUF_FLAG_MASK | BUF_USAGECOUNT_MASK,
2350 : : 0);
2351 : :
2352 : : /*
2353 : : * Remove the buffer from the lookup hashtable, if it was in there.
2354 : : */
2355 [ - + ]: 19008 : if (oldFlags & BM_TAG_VALID)
2356 : 19008 : BufTableDelete(&oldTag, oldHash);
2357 : :
2358 : : /*
2359 : : * Done with mapping lock.
2360 : : */
2361 : 19008 : LWLockRelease(oldPartitionLock);
2362 [ - + ]: 19008 : }
2363 : :
2364 : : /*
2365 : : * Helper routine for GetVictimBuffer()
2366 : : *
2367 : : * Needs to be called on a buffer with a valid tag, pinned, but without the
2368 : : * buffer header spinlock held.
2369 : : *
2370 : : * Returns true if the buffer can be reused, in which case the buffer is only
2371 : : * pinned by this backend and marked as invalid, false otherwise.
2372 : : */
2373 : : static bool
2374 : 1912 : InvalidateVictimBuffer(BufferDesc *buf_hdr)
2375 : : {
2376 : 1912 : uint64 buf_state;
2377 : 1912 : uint32 hash;
2378 : 1912 : LWLock *partition_lock;
2379 : 1912 : BufferTag tag;
2380 : :
2381 [ + - ]: 1912 : Assert(GetPrivateRefCount(BufferDescriptorGetBuffer(buf_hdr)) == 1);
2382 : :
2383 : : /* have buffer pinned, so it's safe to read tag without lock */
2384 : 1912 : tag = buf_hdr->tag;
2385 : :
2386 : 1912 : hash = BufTableHashCode(&tag);
2387 : 1912 : partition_lock = BufMappingPartitionLock(hash);
2388 : :
2389 : 1912 : LWLockAcquire(partition_lock, LW_EXCLUSIVE);
2390 : :
2391 : : /* lock the buffer header */
2392 : 1912 : buf_state = LockBufHdr(buf_hdr);
2393 : :
2394 : : /*
2395 : : * We have the buffer pinned nobody else should have been able to unset
2396 : : * this concurrently.
2397 : : */
2398 [ + - ]: 1912 : Assert(buf_state & BM_TAG_VALID);
2399 [ + - ]: 1912 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
2400 [ + - ]: 1912 : Assert(BufferTagsEqual(&buf_hdr->tag, &tag));
2401 : :
2402 : : /*
2403 : : * If somebody else pinned the buffer since, or even worse, dirtied it,
2404 : : * give up on this buffer: It's clearly in use.
2405 : : */
2406 [ + - - + ]: 1912 : if (BUF_STATE_GET_REFCOUNT(buf_state) != 1 || (buf_state & BM_DIRTY))
2407 : : {
2408 [ # # ]: 0 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
2409 : :
2410 : 0 : UnlockBufHdr(buf_hdr);
2411 : 0 : LWLockRelease(partition_lock);
2412 : :
2413 : 0 : return false;
2414 : : }
2415 : :
2416 : : /*
2417 : : * An invalidated buffer should not have any backends waiting to lock the
2418 : : * buffer, therefore BM_LOCK_WAKE_IN_PROGRESS should not be set.
2419 : : */
2420 [ + - ]: 1912 : Assert(!(buf_state & BM_LOCK_WAKE_IN_PROGRESS));
2421 : :
2422 : : /*
2423 : : * Clear out the buffer's tag and flags and usagecount. This is not
2424 : : * strictly required, as BM_TAG_VALID/BM_VALID needs to be checked before
2425 : : * doing anything with the buffer. But currently it's beneficial, as the
2426 : : * cheaper pre-check for several linear scans of shared buffers use the
2427 : : * tag (see e.g. FlushDatabaseBuffers()).
2428 : : */
2429 : 1912 : ClearBufferTag(&buf_hdr->tag);
2430 : 1912 : UnlockBufHdrExt(buf_hdr, buf_state,
2431 : : 0,
2432 : : BUF_FLAG_MASK | BUF_USAGECOUNT_MASK,
2433 : : 0);
2434 : :
2435 [ + - ]: 1912 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
2436 : :
2437 : : /* finally delete buffer from the buffer mapping table */
2438 : 1912 : BufTableDelete(&tag, hash);
2439 : :
2440 : 1912 : LWLockRelease(partition_lock);
2441 : :
2442 : 1912 : buf_state = pg_atomic_read_u64(&buf_hdr->state);
2443 [ + - ]: 1912 : Assert(!(buf_state & (BM_DIRTY | BM_VALID | BM_TAG_VALID)));
2444 [ + - ]: 1912 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
2445 [ + - ]: 1912 : Assert(BUF_STATE_GET_REFCOUNT(pg_atomic_read_u64(&buf_hdr->state)) > 0);
2446 : :
2447 : 1912 : return true;
2448 : 1912 : }
2449 : :
2450 : : static Buffer
2451 : 40537 : GetVictimBuffer(BufferAccessStrategy strategy, IOContext io_context)
2452 : : {
2453 : 40537 : BufferDesc *buf_hdr;
2454 : 40537 : Buffer buf;
2455 : 40537 : uint64 buf_state;
2456 : 40537 : bool from_ring;
2457 : :
2458 : : /*
2459 : : * Ensure, before we pin a victim buffer, that there's a free refcount
2460 : : * entry and resource owner slot for the pin.
2461 : : */
2462 : 40537 : ReservePrivateRefCountEntry();
2463 : 40537 : ResourceOwnerEnlarge(CurrentResourceOwner);
2464 : :
2465 : : /* we return here if a prospective victim buffer gets used concurrently */
2466 : : again:
2467 : :
2468 : : /*
2469 : : * Select a victim buffer. The buffer is returned pinned and owned by
2470 : : * this backend.
2471 : : */
2472 : 40537 : buf_hdr = StrategyGetBuffer(strategy, &buf_state, &from_ring);
2473 : 40537 : buf = BufferDescriptorGetBuffer(buf_hdr);
2474 : :
2475 : : /*
2476 : : * We shouldn't have any other pins for this buffer.
2477 : : */
2478 : 40537 : CheckBufferIsPinnedOnce(buf);
2479 : :
2480 : : /*
2481 : : * If the buffer was dirty, try to write it out. There is a race
2482 : : * condition here, in that someone might dirty it after we released the
2483 : : * buffer header lock above, or even while we are writing it out (since
2484 : : * our share-lock won't prevent hint-bit updates). We will recheck the
2485 : : * dirty bit after re-locking the buffer header.
2486 : : */
2487 [ + - ]: 40537 : if (buf_state & BM_DIRTY)
2488 : : {
2489 [ # # ]: 0 : Assert(buf_state & BM_TAG_VALID);
2490 [ # # ]: 0 : Assert(buf_state & BM_VALID);
2491 : :
2492 : : /*
2493 : : * We need a share-lock on the buffer contents to write it out (else
2494 : : * we might write invalid data, eg because someone else is compacting
2495 : : * the page contents while we write). We must use a conditional lock
2496 : : * acquisition here to avoid deadlock. Even though the buffer was not
2497 : : * pinned (and therefore surely not locked) when StrategyGetBuffer
2498 : : * returned it, someone else could have pinned and exclusive-locked it
2499 : : * by the time we get here. If we try to get the lock unconditionally,
2500 : : * we'd block waiting for them; if they later block waiting for us,
2501 : : * deadlock ensues. (This has been observed to happen when two
2502 : : * backends are both trying to split btree index pages, and the second
2503 : : * one just happens to be trying to split the page the first one got
2504 : : * from StrategyGetBuffer.)
2505 : : */
2506 [ # # ]: 0 : if (!BufferLockConditional(buf, buf_hdr, BUFFER_LOCK_SHARE))
2507 : : {
2508 : : /*
2509 : : * Someone else has locked the buffer, so give it up and loop back
2510 : : * to get another one.
2511 : : */
2512 : 0 : UnpinBuffer(buf_hdr);
2513 : 0 : goto again;
2514 : : }
2515 : :
2516 : : /*
2517 : : * If using a nondefault strategy, and writing the buffer would
2518 : : * require a WAL flush, let the strategy decide whether to go ahead
2519 : : * and write/reuse the buffer or to choose another victim. We need a
2520 : : * lock to inspect the page LSN, so this can't be done inside
2521 : : * StrategyGetBuffer.
2522 : : */
2523 [ # # ]: 0 : if (strategy != NULL)
2524 : : {
2525 : 0 : XLogRecPtr lsn;
2526 : :
2527 : : /* Read the LSN while holding buffer header lock */
2528 : 0 : buf_state = LockBufHdr(buf_hdr);
2529 : 0 : lsn = BufferGetLSN(buf_hdr);
2530 : 0 : UnlockBufHdr(buf_hdr);
2531 : :
2532 : 0 : if (XLogNeedsFlush(lsn)
2533 [ # # # # ]: 0 : && StrategyRejectBuffer(strategy, buf_hdr, from_ring))
2534 : : {
2535 : 0 : LockBuffer(buf, BUFFER_LOCK_UNLOCK);
2536 : 0 : UnpinBuffer(buf_hdr);
2537 : 0 : goto again;
2538 : : }
2539 [ # # # ]: 0 : }
2540 : :
2541 : : /* OK, do the I/O */
2542 : 0 : FlushBuffer(buf_hdr, NULL, IOOBJECT_RELATION, io_context);
2543 : 0 : LockBuffer(buf, BUFFER_LOCK_UNLOCK);
2544 : :
2545 : 0 : ScheduleBufferTagForWriteback(&BackendWritebackContext, io_context,
2546 : 0 : &buf_hdr->tag);
2547 : 0 : }
2548 : :
2549 : :
2550 [ + + ]: 40537 : if (buf_state & BM_VALID)
2551 : : {
2552 : : /*
2553 : : * When a BufferAccessStrategy is in use, blocks evicted from shared
2554 : : * buffers are counted as IOOP_EVICT in the corresponding context
2555 : : * (e.g. IOCONTEXT_BULKWRITE). Shared buffers are evicted by a
2556 : : * strategy in two cases: 1) while initially claiming buffers for the
2557 : : * strategy ring 2) to replace an existing strategy ring buffer
2558 : : * because it is pinned or in use and cannot be reused.
2559 : : *
2560 : : * Blocks evicted from buffers already in the strategy ring are
2561 : : * counted as IOOP_REUSE in the corresponding strategy context.
2562 : : *
2563 : : * At this point, we can accurately count evictions and reuses,
2564 : : * because we have successfully claimed the valid buffer. Previously,
2565 : : * we may have been forced to release the buffer due to concurrent
2566 : : * pinners or erroring out.
2567 : : */
2568 : 3824 : pgstat_count_io_op(IOOBJECT_RELATION, io_context,
2569 : 1912 : from_ring ? IOOP_REUSE : IOOP_EVICT, 1, 0);
2570 : 1912 : }
2571 : :
2572 : : /*
2573 : : * If the buffer has an entry in the buffer mapping table, delete it. This
2574 : : * can fail because another backend could have pinned or dirtied the
2575 : : * buffer.
2576 : : */
2577 [ + + - + ]: 40537 : if ((buf_state & BM_TAG_VALID) && !InvalidateVictimBuffer(buf_hdr))
2578 : : {
2579 : 0 : UnpinBuffer(buf_hdr);
2580 : 0 : goto again;
2581 : : }
2582 : :
2583 : : /* a final set of sanity checks */
2584 : : #ifdef USE_ASSERT_CHECKING
2585 : 40537 : buf_state = pg_atomic_read_u64(&buf_hdr->state);
2586 : :
2587 [ + - ]: 40537 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) == 1);
2588 [ + - ]: 40537 : Assert(!(buf_state & (BM_TAG_VALID | BM_VALID | BM_DIRTY)));
2589 : :
2590 : 40537 : CheckBufferIsPinnedOnce(buf);
2591 : : #endif
2592 : :
2593 : 81074 : return buf;
2594 : 40537 : }
2595 : :
2596 : : /*
2597 : : * Return the maximum number of buffers that a backend should try to pin once,
2598 : : * to avoid exceeding its fair share. This is the highest value that
2599 : : * GetAdditionalPinLimit() could ever return. Note that it may be zero on a
2600 : : * system with a very small buffer pool relative to max_connections.
2601 : : */
2602 : : uint32
2603 : 346145 : GetPinLimit(void)
2604 : : {
2605 : 346145 : return MaxProportionalPins;
2606 : : }
2607 : :
2608 : : /*
2609 : : * Return the maximum number of additional buffers that this backend should
2610 : : * pin if it wants to stay under the per-backend limit, considering the number
2611 : : * of buffers it has already pinned. Unlike LimitAdditionalPins(), the limit
2612 : : * return by this function can be zero.
2613 : : */
2614 : : uint32
2615 : 796971 : GetAdditionalPinLimit(void)
2616 : : {
2617 : 796971 : uint32 estimated_pins_held;
2618 : :
2619 : : /*
2620 : : * We get the number of "overflowed" pins for free, but don't know the
2621 : : * number of pins in PrivateRefCountArray. The cost of calculating that
2622 : : * exactly doesn't seem worth it, so just assume the max.
2623 : : */
2624 : 796971 : estimated_pins_held = PrivateRefCountOverflowed + REFCOUNT_ARRAY_ENTRIES;
2625 : :
2626 : : /* Is this backend already holding more than its fair share? */
2627 [ - + ]: 796971 : if (estimated_pins_held > MaxProportionalPins)
2628 : 0 : return 0;
2629 : :
2630 : 796971 : return MaxProportionalPins - estimated_pins_held;
2631 : 796971 : }
2632 : :
2633 : : /*
2634 : : * Limit the number of pins a batch operation may additionally acquire, to
2635 : : * avoid running out of pinnable buffers.
2636 : : *
2637 : : * One additional pin is always allowed, on the assumption that the operation
2638 : : * requires at least one to make progress.
2639 : : */
2640 : : void
2641 : 24322 : LimitAdditionalPins(uint32 *additional_pins)
2642 : : {
2643 : 24322 : uint32 limit;
2644 : :
2645 [ + + ]: 24322 : if (*additional_pins <= 1)
2646 : 23645 : return;
2647 : :
2648 : 677 : limit = GetAdditionalPinLimit();
2649 [ + - ]: 677 : limit = Max(limit, 1);
2650 [ + - ]: 677 : if (limit < *additional_pins)
2651 : 0 : *additional_pins = limit;
2652 [ - + ]: 24322 : }
2653 : :
2654 : : /*
2655 : : * Logic shared between ExtendBufferedRelBy(), ExtendBufferedRelTo(). Just to
2656 : : * avoid duplicating the tracing and relpersistence related logic.
2657 : : */
2658 : : static BlockNumber
2659 : 27454 : ExtendBufferedRelCommon(BufferManagerRelation bmr,
2660 : : ForkNumber fork,
2661 : : BufferAccessStrategy strategy,
2662 : : uint32 flags,
2663 : : uint32 extend_by,
2664 : : BlockNumber extend_upto,
2665 : : Buffer *buffers,
2666 : : uint32 *extended_by)
2667 : : {
2668 : 27454 : BlockNumber first_block;
2669 : :
2670 : 27454 : TRACE_POSTGRESQL_BUFFER_EXTEND_START(fork,
2671 : : BMR_GET_SMGR(bmr)->smgr_rlocator.locator.spcOid,
2672 : : BMR_GET_SMGR(bmr)->smgr_rlocator.locator.dbOid,
2673 : : BMR_GET_SMGR(bmr)->smgr_rlocator.locator.relNumber,
2674 : : BMR_GET_SMGR(bmr)->smgr_rlocator.backend,
2675 : : extend_by);
2676 : :
2677 [ + + ]: 27454 : if (bmr.relpersistence == RELPERSISTENCE_TEMP)
2678 : 6264 : first_block = ExtendBufferedRelLocal(bmr, fork, flags,
2679 : 3132 : extend_by, extend_upto,
2680 : 3132 : buffers, &extend_by);
2681 : : else
2682 : 48644 : first_block = ExtendBufferedRelShared(bmr, fork, strategy, flags,
2683 : 24322 : extend_by, extend_upto,
2684 : 24322 : buffers, &extend_by);
2685 : 27454 : *extended_by = extend_by;
2686 : :
2687 : 27454 : TRACE_POSTGRESQL_BUFFER_EXTEND_DONE(fork,
2688 : : BMR_GET_SMGR(bmr)->smgr_rlocator.locator.spcOid,
2689 : : BMR_GET_SMGR(bmr)->smgr_rlocator.locator.dbOid,
2690 : : BMR_GET_SMGR(bmr)->smgr_rlocator.locator.relNumber,
2691 : : BMR_GET_SMGR(bmr)->smgr_rlocator.backend,
2692 : : *extended_by,
2693 : : first_block);
2694 : :
2695 : 54908 : return first_block;
2696 : 27454 : }
2697 : :
2698 : : /*
2699 : : * Implementation of ExtendBufferedRelBy() and ExtendBufferedRelTo() for
2700 : : * shared buffers.
2701 : : */
2702 : : static BlockNumber
2703 : 24322 : ExtendBufferedRelShared(BufferManagerRelation bmr,
2704 : : ForkNumber fork,
2705 : : BufferAccessStrategy strategy,
2706 : : uint32 flags,
2707 : : uint32 extend_by,
2708 : : BlockNumber extend_upto,
2709 : : Buffer *buffers,
2710 : : uint32 *extended_by)
2711 : : {
2712 : 24322 : BlockNumber first_block;
2713 : 24322 : IOContext io_context = IOContextForStrategy(strategy);
2714 : 24322 : instr_time io_start;
2715 : :
2716 : 24322 : LimitAdditionalPins(&extend_by);
2717 : :
2718 : : /*
2719 : : * Acquire victim buffers for extension without holding extension lock.
2720 : : * Writing out victim buffers is the most expensive part of extending the
2721 : : * relation, particularly when doing so requires WAL flushes. Zeroing out
2722 : : * the buffers is also quite expensive, so do that before holding the
2723 : : * extension lock as well.
2724 : : *
2725 : : * These pages are pinned by us and not valid. While we hold the pin they
2726 : : * can't be acquired as victim buffers by another backend.
2727 : : */
2728 [ + + ]: 53395 : for (uint32 i = 0; i < extend_by; i++)
2729 : : {
2730 : 29073 : Block buf_block;
2731 : :
2732 : 29073 : buffers[i] = GetVictimBuffer(strategy, io_context);
2733 : 29073 : buf_block = BufHdrGetBlock(GetBufferDescriptor(buffers[i] - 1));
2734 : :
2735 : : /* new buffers are zero-filled */
2736 [ + - + - : 29073 : MemSet(buf_block, 0, BLCKSZ);
+ - + - #
# ]
2737 : 29073 : }
2738 : :
2739 : : /*
2740 : : * Lock relation against concurrent extensions, unless requested not to.
2741 : : *
2742 : : * We use the same extension lock for all forks. That's unnecessarily
2743 : : * restrictive, but currently extensions for forks don't happen often
2744 : : * enough to make it worth locking more granularly.
2745 : : *
2746 : : * Note that another backend might have extended the relation by the time
2747 : : * we get the lock.
2748 : : */
2749 [ + + ]: 24322 : if (!(flags & EB_SKIP_EXTENSION_LOCK))
2750 : 22646 : LockRelationForExtension(bmr.rel, ExclusiveLock);
2751 : :
2752 : : /*
2753 : : * If requested, invalidate size cache, so that smgrnblocks asks the
2754 : : * kernel.
2755 : : */
2756 [ + + ]: 24322 : if (flags & EB_CLEAR_SIZE_CACHE)
2757 [ + - ]: 715 : BMR_GET_SMGR(bmr)->smgr_cached_nblocks[fork] = InvalidBlockNumber;
2758 : :
2759 [ + - ]: 24322 : first_block = smgrnblocks(BMR_GET_SMGR(bmr), fork);
2760 : :
2761 : : /*
2762 : : * Now that we have the accurate relation size, check if the caller wants
2763 : : * us to extend to only up to a specific size. If there were concurrent
2764 : : * extensions, we might have acquired too many buffers and need to release
2765 : : * them.
2766 : : */
2767 [ + + ]: 24322 : if (extend_upto != InvalidBlockNumber)
2768 : : {
2769 : 715 : uint32 orig_extend_by = extend_by;
2770 : :
2771 [ - + ]: 715 : if (first_block > extend_upto)
2772 : 0 : extend_by = 0;
2773 [ + - ]: 715 : else if ((uint64) first_block + extend_by > extend_upto)
2774 : 0 : extend_by = extend_upto - first_block;
2775 : :
2776 [ - + ]: 715 : for (uint32 i = extend_by; i < orig_extend_by; i++)
2777 : : {
2778 : 0 : BufferDesc *buf_hdr = GetBufferDescriptor(buffers[i] - 1);
2779 : :
2780 : 0 : UnpinBuffer(buf_hdr);
2781 : 0 : }
2782 : :
2783 [ + - ]: 715 : if (extend_by == 0)
2784 : : {
2785 [ # # ]: 0 : if (!(flags & EB_SKIP_EXTENSION_LOCK))
2786 : 0 : UnlockRelationForExtension(bmr.rel, ExclusiveLock);
2787 : 0 : *extended_by = extend_by;
2788 : 0 : return first_block;
2789 : : }
2790 [ - + ]: 715 : }
2791 : :
2792 : : /* Fail if relation is already at maximum possible length */
2793 [ + - ]: 24322 : if ((uint64) first_block + extend_by >= MaxBlockNumber)
2794 [ # # # # : 0 : ereport(ERROR,
# # # # #
# # # ]
2795 : : (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
2796 : : errmsg("cannot extend relation %s beyond %u blocks",
2797 : : relpath(BMR_GET_SMGR(bmr)->smgr_rlocator, fork).str,
2798 : : MaxBlockNumber)));
2799 : :
2800 : : /*
2801 : : * Insert buffers into buffer table, mark as IO_IN_PROGRESS.
2802 : : *
2803 : : * This needs to happen before we extend the relation, because as soon as
2804 : : * we do, other backends can start to read in those pages.
2805 : : */
2806 [ + + ]: 53395 : for (uint32 i = 0; i < extend_by; i++)
2807 : : {
2808 : 29073 : Buffer victim_buf = buffers[i];
2809 : 29073 : BufferDesc *victim_buf_hdr = GetBufferDescriptor(victim_buf - 1);
2810 : 29073 : BufferTag tag;
2811 : 29073 : uint32 hash;
2812 : 29073 : LWLock *partition_lock;
2813 : 29073 : int existing_id;
2814 : :
2815 : : /* in case we need to pin an existing buffer below */
2816 : 29073 : ResourceOwnerEnlarge(CurrentResourceOwner);
2817 : 29073 : ReservePrivateRefCountEntry();
2818 : :
2819 [ + - ]: 29073 : InitBufferTag(&tag, &BMR_GET_SMGR(bmr)->smgr_rlocator.locator, fork,
2820 : 29073 : first_block + i);
2821 : 29073 : hash = BufTableHashCode(&tag);
2822 : 29073 : partition_lock = BufMappingPartitionLock(hash);
2823 : :
2824 : 29073 : LWLockAcquire(partition_lock, LW_EXCLUSIVE);
2825 : :
2826 : 29073 : existing_id = BufTableInsert(&tag, hash, victim_buf_hdr->buf_id);
2827 : :
2828 : : /*
2829 : : * We get here only in the corner case where we are trying to extend
2830 : : * the relation but we found a pre-existing buffer. This can happen
2831 : : * because a prior attempt at extending the relation failed, and
2832 : : * because mdread doesn't complain about reads beyond EOF (when
2833 : : * zero_damaged_pages is ON) and so a previous attempt to read a block
2834 : : * beyond EOF could have left a "valid" zero-filled buffer.
2835 : : *
2836 : : * This has also been observed when relation was overwritten by
2837 : : * external process. Since the legitimate cases should always have
2838 : : * left a zero-filled buffer, complain if not PageIsNew.
2839 : : */
2840 [ - + ]: 29073 : if (existing_id >= 0)
2841 : : {
2842 : 0 : BufferDesc *existing_hdr = GetBufferDescriptor(existing_id);
2843 : 0 : Block buf_block;
2844 : 0 : bool valid;
2845 : :
2846 : : /*
2847 : : * Pin the existing buffer before releasing the partition lock,
2848 : : * preventing it from being evicted.
2849 : : */
2850 : 0 : valid = PinBuffer(existing_hdr, strategy, false);
2851 : :
2852 : 0 : LWLockRelease(partition_lock);
2853 : 0 : UnpinBuffer(victim_buf_hdr);
2854 : :
2855 : 0 : buffers[i] = BufferDescriptorGetBuffer(existing_hdr);
2856 : 0 : buf_block = BufHdrGetBlock(existing_hdr);
2857 : :
2858 [ # # # # ]: 0 : if (valid && !PageIsNew((Page) buf_block))
2859 [ # # # # : 0 : ereport(ERROR,
# # # # #
# # # ]
2860 : : (errmsg("unexpected data beyond EOF in block %u of relation \"%s\"",
2861 : : existing_hdr->tag.blockNum,
2862 : : relpath(BMR_GET_SMGR(bmr)->smgr_rlocator, fork).str)));
2863 : :
2864 : : /*
2865 : : * We *must* do smgr[zero]extend before succeeding, else the page
2866 : : * will not be reserved by the kernel, and the next P_NEW call
2867 : : * will decide to return the same page. Clear the BM_VALID bit,
2868 : : * do StartBufferIO() and proceed.
2869 : : *
2870 : : * Loop to handle the very small possibility that someone re-sets
2871 : : * BM_VALID between our clearing it and StartBufferIO inspecting
2872 : : * it.
2873 : : */
2874 : 0 : do
2875 : : {
2876 : 0 : pg_atomic_fetch_and_u64(&existing_hdr->state, ~BM_VALID);
2877 [ # # ]: 0 : } while (!StartBufferIO(existing_hdr, true, false));
2878 : 0 : }
2879 : : else
2880 : : {
2881 : 29073 : uint64 buf_state;
2882 : 29073 : uint64 set_bits = 0;
2883 : :
2884 : 29073 : buf_state = LockBufHdr(victim_buf_hdr);
2885 : :
2886 : : /* some sanity checks while we hold the buffer header lock */
2887 [ + - ]: 29073 : Assert(!(buf_state & (BM_VALID | BM_TAG_VALID | BM_DIRTY | BM_JUST_DIRTIED)));
2888 [ - + ]: 29073 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) == 1);
2889 : :
2890 : 29073 : victim_buf_hdr->tag = tag;
2891 : :
2892 : 29073 : set_bits |= BM_TAG_VALID | BUF_USAGECOUNT_ONE;
2893 [ + + + + ]: 29073 : if (bmr.relpersistence == RELPERSISTENCE_PERMANENT || fork == INIT_FORKNUM)
2894 : 29029 : set_bits |= BM_PERMANENT;
2895 : :
2896 : 58146 : UnlockBufHdrExt(victim_buf_hdr, buf_state,
2897 : 29073 : set_bits, 0,
2898 : : 0);
2899 : :
2900 : 29073 : LWLockRelease(partition_lock);
2901 : :
2902 : : /* XXX: could combine the locked operations in it with the above */
2903 : 29073 : StartBufferIO(victim_buf_hdr, true, false);
2904 : 29073 : }
2905 : 29073 : }
2906 : :
2907 : 24322 : io_start = pgstat_prepare_io_time(track_io_timing);
2908 : :
2909 : : /*
2910 : : * Note: if smgrzeroextend fails, we will end up with buffers that are
2911 : : * allocated but not marked BM_VALID. The next relation extension will
2912 : : * still select the same block number (because the relation didn't get any
2913 : : * longer on disk) and so future attempts to extend the relation will find
2914 : : * the same buffers (if they have not been recycled) but come right back
2915 : : * here to try smgrzeroextend again.
2916 : : *
2917 : : * We don't need to set checksum for all-zero pages.
2918 : : */
2919 [ + - ]: 24322 : smgrzeroextend(BMR_GET_SMGR(bmr), fork, first_block, extend_by, false);
2920 : :
2921 : : /*
2922 : : * Release the file-extension lock; it's now OK for someone else to extend
2923 : : * the relation some more.
2924 : : *
2925 : : * We remove IO_IN_PROGRESS after this, as waking up waiting backends can
2926 : : * take noticeable time.
2927 : : */
2928 [ + + ]: 24322 : if (!(flags & EB_SKIP_EXTENSION_LOCK))
2929 : 22646 : UnlockRelationForExtension(bmr.rel, ExclusiveLock);
2930 : :
2931 : 48644 : pgstat_count_io_op_time(IOOBJECT_RELATION, io_context, IOOP_EXTEND,
2932 : 24322 : io_start, 1, extend_by * BLCKSZ);
2933 : :
2934 : : /* Set BM_VALID, terminate IO, and wake up any waiters */
2935 [ + + ]: 53395 : for (uint32 i = 0; i < extend_by; i++)
2936 : : {
2937 : 29073 : Buffer buf = buffers[i];
2938 : 29073 : BufferDesc *buf_hdr = GetBufferDescriptor(buf - 1);
2939 : 29073 : bool lock = false;
2940 : :
2941 [ + + + + ]: 29073 : if (flags & EB_LOCK_FIRST && i == 0)
2942 : 23546 : lock = true;
2943 [ + - ]: 5527 : else if (flags & EB_LOCK_TARGET)
2944 : : {
2945 [ # # ]: 0 : Assert(extend_upto != InvalidBlockNumber);
2946 [ # # ]: 0 : if (first_block + i + 1 == extend_upto)
2947 : 0 : lock = true;
2948 : 0 : }
2949 : :
2950 [ + + ]: 29073 : if (lock)
2951 : 23546 : LockBuffer(buf, BUFFER_LOCK_EXCLUSIVE);
2952 : :
2953 : 29073 : TerminateBufferIO(buf_hdr, false, BM_VALID, true, false);
2954 : 29073 : }
2955 : :
2956 : 24322 : pgBufferUsage.shared_blks_written += extend_by;
2957 : :
2958 : 24322 : *extended_by = extend_by;
2959 : :
2960 : 24322 : return first_block;
2961 : 24322 : }
2962 : :
2963 : : /*
2964 : : * BufferIsLockedByMe
2965 : : *
2966 : : * Checks if this backend has the buffer locked in any mode.
2967 : : *
2968 : : * Buffer must be pinned.
2969 : : */
2970 : : bool
2971 : 1862163 : BufferIsLockedByMe(Buffer buffer)
2972 : : {
2973 : 1862163 : BufferDesc *bufHdr;
2974 : :
2975 [ - + # # : 1862163 : Assert(BufferIsPinned(buffer));
- + ]
2976 : :
2977 [ + - ]: 1862163 : if (BufferIsLocal(buffer))
2978 : : {
2979 : : /* Content locks are not maintained for local buffers. */
2980 : 0 : return true;
2981 : : }
2982 : : else
2983 : : {
2984 : 1862163 : bufHdr = GetBufferDescriptor(buffer - 1);
2985 : 1862163 : return BufferLockHeldByMe(bufHdr);
2986 : : }
2987 : 1862163 : }
2988 : :
2989 : : /*
2990 : : * BufferIsLockedByMeInMode
2991 : : *
2992 : : * Checks if this backend has the buffer locked in the specified mode.
2993 : : *
2994 : : * Buffer must be pinned.
2995 : : */
2996 : : bool
2997 : 8621338 : BufferIsLockedByMeInMode(Buffer buffer, BufferLockMode mode)
2998 : : {
2999 : 8621338 : BufferDesc *bufHdr;
3000 : :
3001 [ - + # # : 8621338 : Assert(BufferIsPinned(buffer));
+ + ]
3002 : :
3003 [ + + ]: 8621338 : if (BufferIsLocal(buffer))
3004 : : {
3005 : : /* Content locks are not maintained for local buffers. */
3006 : 253 : return true;
3007 : : }
3008 : : else
3009 : : {
3010 : 8621085 : bufHdr = GetBufferDescriptor(buffer - 1);
3011 : 8621085 : return BufferLockHeldByMeInMode(bufHdr, mode);
3012 : : }
3013 : 8621338 : }
3014 : :
3015 : : /*
3016 : : * BufferIsDirty
3017 : : *
3018 : : * Checks if buffer is already dirty.
3019 : : *
3020 : : * Buffer must be pinned and exclusive-locked. (Without an exclusive lock,
3021 : : * the result may be stale before it's returned.)
3022 : : */
3023 : : bool
3024 : 2592503 : BufferIsDirty(Buffer buffer)
3025 : : {
3026 : 2592503 : BufferDesc *bufHdr;
3027 : :
3028 [ - + # # : 2592503 : Assert(BufferIsPinned(buffer));
- + ]
3029 : :
3030 [ + - ]: 2592503 : if (BufferIsLocal(buffer))
3031 : : {
3032 : 0 : int bufid = -buffer - 1;
3033 : :
3034 : 0 : bufHdr = GetLocalBufferDescriptor(bufid);
3035 : : /* Content locks are not maintained for local buffers. */
3036 : 0 : }
3037 : : else
3038 : : {
3039 : 2592503 : bufHdr = GetBufferDescriptor(buffer - 1);
3040 [ + - ]: 2592503 : Assert(BufferIsLockedByMeInMode(buffer, BUFFER_LOCK_EXCLUSIVE));
3041 : : }
3042 : :
3043 : 5185006 : return pg_atomic_read_u64(&bufHdr->state) & BM_DIRTY;
3044 : 2592503 : }
3045 : :
3046 : : /*
3047 : : * MarkBufferDirty
3048 : : *
3049 : : * Marks buffer contents as dirty (actual write happens later).
3050 : : *
3051 : : * Buffer must be pinned and exclusive-locked. (If caller does not hold
3052 : : * exclusive lock, then somebody could be in process of writing the buffer,
3053 : : * leading to risk of bad data written to disk.)
3054 : : */
3055 : : void
3056 : 3777801 : MarkBufferDirty(Buffer buffer)
3057 : : {
3058 : 3777801 : BufferDesc *bufHdr;
3059 : 3777801 : uint64 buf_state;
3060 : 3777801 : uint64 old_buf_state;
3061 : :
3062 [ + - ]: 3777801 : if (!BufferIsValid(buffer))
3063 [ # # # # ]: 0 : elog(ERROR, "bad buffer ID: %d", buffer);
3064 : :
3065 [ + + ]: 3777801 : if (BufferIsLocal(buffer))
3066 : : {
3067 : 340295 : MarkLocalBufferDirty(buffer);
3068 : 340295 : return;
3069 : : }
3070 : :
3071 : 3437506 : bufHdr = GetBufferDescriptor(buffer - 1);
3072 : :
3073 [ - + # # : 3437506 : Assert(BufferIsPinned(buffer));
- + ]
3074 [ + - ]: 3437506 : Assert(BufferIsLockedByMeInMode(buffer, BUFFER_LOCK_EXCLUSIVE));
3075 : :
3076 : : /*
3077 : : * NB: We have to wait for the buffer header spinlock to be not held, as
3078 : : * TerminateBufferIO() relies on the spinlock.
3079 : : */
3080 : 3437506 : old_buf_state = pg_atomic_read_u64(&bufHdr->state);
3081 : 3437611 : for (;;)
3082 : : {
3083 [ + + ]: 3437611 : if (old_buf_state & BM_LOCKED)
3084 : 103 : old_buf_state = WaitBufHdrUnlocked(bufHdr);
3085 : :
3086 : 3437611 : buf_state = old_buf_state;
3087 : :
3088 [ + - ]: 3437611 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
3089 : 3437611 : buf_state |= BM_DIRTY | BM_JUST_DIRTIED;
3090 : :
3091 [ + + + + ]: 6875222 : if (pg_atomic_compare_exchange_u64(&bufHdr->state, &old_buf_state,
3092 : 3437611 : buf_state))
3093 : 3437506 : break;
3094 : : }
3095 : :
3096 : : /*
3097 : : * If the buffer was not dirty already, do vacuum accounting.
3098 : : */
3099 [ + + ]: 3437506 : if (!(old_buf_state & BM_DIRTY))
3100 : : {
3101 : 38155 : pgBufferUsage.shared_blks_dirtied++;
3102 [ + - ]: 38155 : if (VacuumCostActive)
3103 : 0 : VacuumCostBalance += VacuumCostPageDirty;
3104 : 38155 : }
3105 [ - + ]: 3777801 : }
3106 : :
3107 : : /*
3108 : : * ReleaseAndReadBuffer -- combine ReleaseBuffer() and ReadBuffer()
3109 : : *
3110 : : * Formerly, this saved one cycle of acquiring/releasing the BufMgrLock
3111 : : * compared to calling the two routines separately. Now it's mainly just
3112 : : * a convenience function. However, if the passed buffer is valid and
3113 : : * already contains the desired block, we just return it as-is; and that
3114 : : * does save considerable work compared to a full release and reacquire.
3115 : : *
3116 : : * Note: it is OK to pass buffer == InvalidBuffer, indicating that no old
3117 : : * buffer actually needs to be released. This case is the same as ReadBuffer,
3118 : : * but can save some tests in the caller.
3119 : : */
3120 : : Buffer
3121 : 5393321 : ReleaseAndReadBuffer(Buffer buffer,
3122 : : Relation relation,
3123 : : BlockNumber blockNum)
3124 : : {
3125 : 5393321 : ForkNumber forkNum = MAIN_FORKNUM;
3126 : 5393321 : BufferDesc *bufHdr;
3127 : :
3128 [ + + ]: 5393321 : if (BufferIsValid(buffer))
3129 : : {
3130 [ - + # # : 2815268 : Assert(BufferIsPinned(buffer));
+ + ]
3131 [ + + ]: 2815268 : if (BufferIsLocal(buffer))
3132 : : {
3133 : 12277 : bufHdr = GetLocalBufferDescriptor(-buffer - 1);
3134 [ + + ]: 12277 : if (bufHdr->tag.blockNum == blockNum &&
3135 [ + - - + ]: 1166 : BufTagMatchesRelFileLocator(&bufHdr->tag, &relation->rd_locator) &&
3136 : 1166 : BufTagGetForkNum(&bufHdr->tag) == forkNum)
3137 : 1166 : return buffer;
3138 : 11111 : UnpinLocalBuffer(buffer);
3139 : 11111 : }
3140 : : else
3141 : : {
3142 : 2802991 : bufHdr = GetBufferDescriptor(buffer - 1);
3143 : : /* we have pin, so it's ok to examine tag without spinlock */
3144 [ + + ]: 2802991 : if (bufHdr->tag.blockNum == blockNum &&
3145 [ + - - + ]: 877924 : BufTagMatchesRelFileLocator(&bufHdr->tag, &relation->rd_locator) &&
3146 : 877924 : BufTagGetForkNum(&bufHdr->tag) == forkNum)
3147 : 877924 : return buffer;
3148 : 1925067 : UnpinBuffer(bufHdr);
3149 : : }
3150 : 1936178 : }
3151 : :
3152 : 4514231 : return ReadBuffer(relation, blockNum);
3153 : 5393321 : }
3154 : :
3155 : : /*
3156 : : * PinBuffer -- make buffer unavailable for replacement.
3157 : : *
3158 : : * For the default access strategy, the buffer's usage_count is incremented
3159 : : * when we first pin it; for other strategies we just make sure the usage_count
3160 : : * isn't zero. (The idea of the latter is that we don't want synchronized
3161 : : * heap scans to inflate the count, but we need it to not be zero to discourage
3162 : : * other backends from stealing buffers from our ring. As long as we cycle
3163 : : * through the ring faster than the global clock-sweep cycles, buffers in
3164 : : * our ring won't be chosen as victims for replacement by other backends.)
3165 : : *
3166 : : * This should be applied only to shared buffers, never local ones.
3167 : : *
3168 : : * Since buffers are pinned/unpinned very frequently, pin buffers without
3169 : : * taking the buffer header lock; instead update the state variable in loop of
3170 : : * CAS operations. Hopefully it's just a single CAS.
3171 : : *
3172 : : * Note that ResourceOwnerEnlarge() and ReservePrivateRefCountEntry()
3173 : : * must have been done already.
3174 : : *
3175 : : * Returns true if buffer is BM_VALID, else false. This provision allows
3176 : : * some callers to avoid an extra spinlock cycle. If skip_if_not_valid is
3177 : : * true, then a false return value also indicates that the buffer was
3178 : : * (recently) invalid and has not been pinned.
3179 : : */
3180 : : static bool
3181 : 11321558 : PinBuffer(BufferDesc *buf, BufferAccessStrategy strategy,
3182 : : bool skip_if_not_valid)
3183 : : {
3184 : 11321558 : Buffer b = BufferDescriptorGetBuffer(buf);
3185 : 11321558 : bool result;
3186 : 11321558 : PrivateRefCountEntry *ref;
3187 : :
3188 [ + - ]: 11321558 : Assert(!BufferIsLocal(b));
3189 [ + - ]: 11321558 : Assert(ReservedRefCountSlot != -1);
3190 : :
3191 : 11321558 : ref = GetPrivateRefCountEntry(b, true);
3192 : :
3193 [ + + ]: 11321558 : if (ref == NULL)
3194 : : {
3195 : 10594240 : uint64 buf_state;
3196 : 10594240 : uint64 old_buf_state;
3197 : :
3198 : 10594240 : old_buf_state = pg_atomic_read_u64(&buf->state);
3199 : 10596920 : for (;;)
3200 : : {
3201 [ + - + - ]: 10596920 : if (unlikely(skip_if_not_valid && !(old_buf_state & BM_VALID)))
3202 : 0 : return false;
3203 : :
3204 : : /*
3205 : : * We're not allowed to increase the refcount while the buffer
3206 : : * header spinlock is held. Wait for the lock to be released.
3207 : : */
3208 [ + + ]: 10596920 : if (old_buf_state & BM_LOCKED)
3209 : 92 : old_buf_state = WaitBufHdrUnlocked(buf);
3210 : :
3211 : 10596920 : buf_state = old_buf_state;
3212 : :
3213 : : /* increase refcount */
3214 : 10596920 : buf_state += BUF_REFCOUNT_ONE;
3215 : :
3216 [ + + ]: 10596920 : if (strategy == NULL)
3217 : : {
3218 : : /* Default case: increase usagecount unless already max. */
3219 [ + + ]: 10551331 : if (BUF_STATE_GET_USAGECOUNT(buf_state) < BM_MAX_USAGE_COUNT)
3220 : 121648 : buf_state += BUF_USAGECOUNT_ONE;
3221 : 10551331 : }
3222 : : else
3223 : : {
3224 : : /*
3225 : : * Ring buffers shouldn't evict others from pool. Thus we
3226 : : * don't make usagecount more than 1.
3227 : : */
3228 [ - + ]: 45589 : if (BUF_STATE_GET_USAGECOUNT(buf_state) == 0)
3229 : 0 : buf_state += BUF_USAGECOUNT_ONE;
3230 : : }
3231 : :
3232 [ + + + + ]: 21193840 : if (pg_atomic_compare_exchange_u64(&buf->state, &old_buf_state,
3233 : 10596920 : buf_state))
3234 : : {
3235 : 10594240 : result = (buf_state & BM_VALID) != 0;
3236 : :
3237 : 10594240 : TrackNewBufferPin(b);
3238 : 10594240 : break;
3239 : : }
3240 : : }
3241 [ - + ]: 10594240 : }
3242 : : else
3243 : : {
3244 : : /*
3245 : : * If we previously pinned the buffer, it is likely to be valid, but
3246 : : * it may not be if StartReadBuffers() was called and
3247 : : * WaitReadBuffers() hasn't been called yet. We'll check by loading
3248 : : * the flags without locking. This is racy, but it's OK to return
3249 : : * false spuriously: when WaitReadBuffers() calls StartBufferIO(),
3250 : : * it'll see that it's now valid.
3251 : : *
3252 : : * Note: We deliberately avoid a Valgrind client request here.
3253 : : * Individual access methods can optionally superimpose buffer page
3254 : : * client requests on top of our client requests to enforce that
3255 : : * buffers are only accessed while locked (and pinned). It's possible
3256 : : * that the buffer page is legitimately non-accessible here. We
3257 : : * cannot meddle with that.
3258 : : */
3259 : 727318 : result = (pg_atomic_read_u64(&buf->state) & BM_VALID) != 0;
3260 : :
3261 [ + - ]: 727318 : Assert(ref->data.refcount > 0);
3262 : 727318 : ref->data.refcount++;
3263 : 727318 : ResourceOwnerRememberBuffer(CurrentResourceOwner, b);
3264 : : }
3265 : :
3266 : 11321558 : return result;
3267 : 11321558 : }
3268 : :
3269 : : /*
3270 : : * PinBuffer_Locked -- as above, but caller already locked the buffer header.
3271 : : * The spinlock is released before return.
3272 : : *
3273 : : * As this function is called with the spinlock held, the caller has to
3274 : : * previously call ReservePrivateRefCountEntry() and
3275 : : * ResourceOwnerEnlarge(CurrentResourceOwner);
3276 : : *
3277 : : * Currently, no callers of this function want to modify the buffer's
3278 : : * usage_count at all, so there's no need for a strategy parameter.
3279 : : * Also we don't bother with a BM_VALID test (the caller could check that for
3280 : : * itself).
3281 : : *
3282 : : * Also all callers only ever use this function when it's known that the
3283 : : * buffer can't have a preexisting pin by this backend. That allows us to skip
3284 : : * searching the private refcount array & hash, which is a boon, because the
3285 : : * spinlock is still held.
3286 : : *
3287 : : * Note: use of this routine is frequently mandatory, not just an optimization
3288 : : * to save a spin lock/unlock cycle, because we need to pin a buffer before
3289 : : * its state can change under us.
3290 : : */
3291 : : static void
3292 : 6998 : PinBuffer_Locked(BufferDesc *buf)
3293 : : {
3294 : 6998 : uint64 old_buf_state;
3295 : :
3296 : : /*
3297 : : * As explained, We don't expect any preexisting pins. That allows us to
3298 : : * manipulate the PrivateRefCount after releasing the spinlock
3299 : : */
3300 [ + - ]: 6998 : Assert(GetPrivateRefCountEntry(BufferDescriptorGetBuffer(buf), false) == NULL);
3301 : :
3302 : : /*
3303 : : * Since we hold the buffer spinlock, we can update the buffer state and
3304 : : * release the lock in one operation.
3305 : : */
3306 : 6998 : old_buf_state = pg_atomic_read_u64(&buf->state);
3307 : :
3308 : 6998 : UnlockBufHdrExt(buf, old_buf_state,
3309 : : 0, 0, 1);
3310 : :
3311 : 6998 : TrackNewBufferPin(BufferDescriptorGetBuffer(buf));
3312 : 6998 : }
3313 : :
3314 : : /*
3315 : : * Support for waking up another backend that is waiting for the cleanup lock
3316 : : * to be released using BM_PIN_COUNT_WAITER.
3317 : : *
3318 : : * See LockBufferForCleanup().
3319 : : *
3320 : : * Expected to be called just after releasing a buffer pin (in a BufferDesc,
3321 : : * not just reducing the backend-local pincount for the buffer).
3322 : : */
3323 : : static void
3324 : 0 : WakePinCountWaiter(BufferDesc *buf)
3325 : : {
3326 : : /*
3327 : : * Acquire the buffer header lock, re-check that there's a waiter. Another
3328 : : * backend could have unpinned this buffer, and already woken up the
3329 : : * waiter.
3330 : : *
3331 : : * There's no danger of the buffer being replaced after we unpinned it
3332 : : * above, as it's pinned by the waiter. The waiter removes
3333 : : * BM_PIN_COUNT_WAITER if it stops waiting for a reason other than this
3334 : : * backend waking it up.
3335 : : */
3336 : 0 : uint64 buf_state = LockBufHdr(buf);
3337 : :
3338 [ # # # # ]: 0 : if ((buf_state & BM_PIN_COUNT_WAITER) &&
3339 : 0 : BUF_STATE_GET_REFCOUNT(buf_state) == 1)
3340 : : {
3341 : : /* we just released the last pin other than the waiter's */
3342 : 0 : int wait_backend_pgprocno = buf->wait_backend_pgprocno;
3343 : :
3344 : 0 : UnlockBufHdrExt(buf, buf_state,
3345 : : 0, BM_PIN_COUNT_WAITER,
3346 : : 0);
3347 : 0 : ProcSendSignal(wait_backend_pgprocno);
3348 : 0 : }
3349 : : else
3350 : 0 : UnlockBufHdr(buf);
3351 : 0 : }
3352 : :
3353 : : /*
3354 : : * UnpinBuffer -- make buffer available for replacement.
3355 : : *
3356 : : * This should be applied only to shared buffers, never local ones. This
3357 : : * always adjusts CurrentResourceOwner.
3358 : : */
3359 : : static void
3360 : 13667167 : UnpinBuffer(BufferDesc *buf)
3361 : : {
3362 : 13667167 : Buffer b = BufferDescriptorGetBuffer(buf);
3363 : :
3364 : 13667167 : ResourceOwnerForgetBuffer(CurrentResourceOwner, b);
3365 : 13667167 : UnpinBufferNoOwner(buf);
3366 : 13667167 : }
3367 : :
3368 : : static void
3369 : 13668372 : UnpinBufferNoOwner(BufferDesc *buf)
3370 : : {
3371 : 13668372 : PrivateRefCountEntry *ref;
3372 : 13668372 : Buffer b = BufferDescriptorGetBuffer(buf);
3373 : :
3374 [ + - ]: 13668372 : Assert(!BufferIsLocal(b));
3375 : :
3376 : : /* not moving as we're likely deleting it soon anyway */
3377 : 13668372 : ref = GetPrivateRefCountEntry(b, false);
3378 [ + - ]: 13668372 : Assert(ref != NULL);
3379 [ + - ]: 13668372 : Assert(ref->data.refcount > 0);
3380 : 13668372 : ref->data.refcount--;
3381 [ + + ]: 13668372 : if (ref->data.refcount == 0)
3382 : : {
3383 : 10641775 : uint64 old_buf_state;
3384 : :
3385 : : /*
3386 : : * Mark buffer non-accessible to Valgrind.
3387 : : *
3388 : : * Note that the buffer may have already been marked non-accessible
3389 : : * within access method code that enforces that buffers are only
3390 : : * accessed while a buffer lock is held.
3391 : : */
3392 : 10641775 : VALGRIND_MAKE_MEM_NOACCESS(BufHdrGetBlock(buf), BLCKSZ);
3393 : :
3394 : : /*
3395 : : * I'd better not still hold the buffer content lock. Can't use
3396 : : * BufferIsLockedByMe(), as that asserts the buffer is pinned.
3397 : : */
3398 [ + - ]: 10641775 : Assert(!BufferLockHeldByMe(buf));
3399 : :
3400 : : /* decrement the shared reference count */
3401 : 10641775 : old_buf_state = pg_atomic_fetch_sub_u64(&buf->state, BUF_REFCOUNT_ONE);
3402 : :
3403 : : /* Support LockBufferForCleanup() */
3404 [ + - ]: 10641775 : if (old_buf_state & BM_PIN_COUNT_WAITER)
3405 : 0 : WakePinCountWaiter(buf);
3406 : :
3407 : 10641775 : ForgetPrivateRefCountEntry(ref);
3408 : 10641775 : }
3409 : 13668372 : }
3410 : :
3411 : : /*
3412 : : * Set up backend-local tracking of a buffer pinned the first time by this
3413 : : * backend.
3414 : : */
3415 : : inline void
3416 : 10641775 : TrackNewBufferPin(Buffer buf)
3417 : : {
3418 : 10641775 : PrivateRefCountEntry *ref;
3419 : :
3420 : 10641775 : ref = NewPrivateRefCountEntry(buf);
3421 : 10641775 : ref->data.refcount++;
3422 : :
3423 : 10641775 : ResourceOwnerRememberBuffer(CurrentResourceOwner, buf);
3424 : :
3425 : : /*
3426 : : * This is the first pin for this page by this backend, mark its page as
3427 : : * defined to valgrind. While the page contents might not actually be
3428 : : * valid yet, we don't currently guarantee that such pages are marked
3429 : : * undefined or non-accessible.
3430 : : *
3431 : : * It's not necessarily the prettiest to do this here, but otherwise we'd
3432 : : * need this block of code in multiple places.
3433 : : */
3434 : 10641775 : VALGRIND_MAKE_MEM_DEFINED(BufHdrGetBlock(GetBufferDescriptor(buf - 1)),
3435 : : BLCKSZ);
3436 : 10641775 : }
3437 : :
3438 : : #define ST_SORT sort_checkpoint_bufferids
3439 : : #define ST_ELEMENT_TYPE CkptSortItem
3440 : : #define ST_COMPARE(a, b) ckpt_buforder_comparator(a, b)
3441 : : #define ST_SCOPE static
3442 : : #define ST_DEFINE
3443 : : #include "lib/sort_template.h"
3444 : :
3445 : : /*
3446 : : * BufferSync -- Write out all dirty buffers in the pool.
3447 : : *
3448 : : * This is called at checkpoint time to write out all dirty shared buffers.
3449 : : * The checkpoint request flags should be passed in. If CHECKPOINT_FAST is
3450 : : * set, we disable delays between writes; if CHECKPOINT_IS_SHUTDOWN,
3451 : : * CHECKPOINT_END_OF_RECOVERY or CHECKPOINT_FLUSH_UNLOGGED is set, we write
3452 : : * even unlogged buffers, which are otherwise skipped. The remaining flags
3453 : : * currently have no effect here.
3454 : : */
3455 : : static void
3456 : 7 : BufferSync(int flags)
3457 : : {
3458 : 7 : uint64 buf_state;
3459 : 7 : int buf_id;
3460 : 7 : int num_to_scan;
3461 : 7 : int num_spaces;
3462 : 7 : int num_processed;
3463 : 7 : int num_written;
3464 : 7 : CkptTsStatus *per_ts_stat = NULL;
3465 : 7 : Oid last_tsid;
3466 : 7 : binaryheap *ts_heap;
3467 : 7 : int i;
3468 : 7 : uint64 mask = BM_DIRTY;
3469 : 7 : WritebackContext wb_context;
3470 : :
3471 : : /*
3472 : : * Unless this is a shutdown checkpoint or we have been explicitly told,
3473 : : * we write only permanent, dirty buffers. But at shutdown or end of
3474 : : * recovery, we write all dirty buffers.
3475 : : */
3476 [ + + ]: 7 : if (!((flags & (CHECKPOINT_IS_SHUTDOWN | CHECKPOINT_END_OF_RECOVERY |
3477 : : CHECKPOINT_FLUSH_UNLOGGED))))
3478 : 2 : mask |= BM_PERMANENT;
3479 : :
3480 : : /*
3481 : : * Loop over all buffers, and mark the ones that need to be written with
3482 : : * BM_CHECKPOINT_NEEDED. Count them as we go (num_to_scan), so that we
3483 : : * can estimate how much work needs to be done.
3484 : : *
3485 : : * This allows us to write only those pages that were dirty when the
3486 : : * checkpoint began, and not those that get dirtied while it proceeds.
3487 : : * Whenever a page with BM_CHECKPOINT_NEEDED is written out, either by us
3488 : : * later in this function, or by normal backends or the bgwriter cleaning
3489 : : * scan, the flag is cleared. Any buffer dirtied after this point won't
3490 : : * have the flag set.
3491 : : *
3492 : : * Note that if we fail to write some buffer, we may leave buffers with
3493 : : * BM_CHECKPOINT_NEEDED still set. This is OK since any such buffer would
3494 : : * certainly need to be written for the next checkpoint attempt, too.
3495 : : */
3496 : 7 : num_to_scan = 0;
3497 [ + + ]: 114695 : for (buf_id = 0; buf_id < NBuffers; buf_id++)
3498 : : {
3499 : 114688 : BufferDesc *bufHdr = GetBufferDescriptor(buf_id);
3500 : 114688 : uint64 set_bits = 0;
3501 : :
3502 : : /*
3503 : : * Header spinlock is enough to examine BM_DIRTY, see comment in
3504 : : * SyncOneBuffer.
3505 : : */
3506 : 114688 : buf_state = LockBufHdr(bufHdr);
3507 : :
3508 [ + + ]: 114688 : if ((buf_state & mask) == mask)
3509 : : {
3510 : 5230 : CkptSortItem *item;
3511 : :
3512 : 5230 : set_bits = BM_CHECKPOINT_NEEDED;
3513 : :
3514 : 5230 : item = &CkptBufferIds[num_to_scan++];
3515 : 5230 : item->buf_id = buf_id;
3516 : 5230 : item->tsId = bufHdr->tag.spcOid;
3517 : 5230 : item->relNumber = BufTagGetRelNumber(&bufHdr->tag);
3518 : 5230 : item->forkNum = BufTagGetForkNum(&bufHdr->tag);
3519 : 5230 : item->blockNum = bufHdr->tag.blockNum;
3520 : 5230 : }
3521 : :
3522 : 229376 : UnlockBufHdrExt(bufHdr, buf_state,
3523 : 114688 : set_bits, 0,
3524 : : 0);
3525 : :
3526 : : /* Check for barrier events in case NBuffers is large. */
3527 [ + - ]: 114688 : if (ProcSignalBarrierPending)
3528 : 0 : ProcessProcSignalBarrier();
3529 : 114688 : }
3530 : :
3531 [ + + ]: 7 : if (num_to_scan == 0)
3532 : 2 : return; /* nothing to do */
3533 : :
3534 : 5 : WritebackContextInit(&wb_context, &checkpoint_flush_after);
3535 : :
3536 : 5 : TRACE_POSTGRESQL_BUFFER_SYNC_START(NBuffers, num_to_scan);
3537 : :
3538 : : /*
3539 : : * Sort buffers that need to be written to reduce the likelihood of random
3540 : : * IO. The sorting is also important for the implementation of balancing
3541 : : * writes between tablespaces. Without balancing writes we'd potentially
3542 : : * end up writing to the tablespaces one-by-one; possibly overloading the
3543 : : * underlying system.
3544 : : */
3545 : 5 : sort_checkpoint_bufferids(CkptBufferIds, num_to_scan);
3546 : :
3547 : 5 : num_spaces = 0;
3548 : :
3549 : : /*
3550 : : * Allocate progress status for each tablespace with buffers that need to
3551 : : * be flushed. This requires the to-be-flushed array to be sorted.
3552 : : */
3553 : 5 : last_tsid = InvalidOid;
3554 [ + + ]: 5235 : for (i = 0; i < num_to_scan; i++)
3555 : : {
3556 : 5230 : CkptTsStatus *s;
3557 : 5230 : Oid cur_tsid;
3558 : :
3559 : 5230 : cur_tsid = CkptBufferIds[i].tsId;
3560 : :
3561 : : /*
3562 : : * Grow array of per-tablespace status structs, every time a new
3563 : : * tablespace is found.
3564 : : */
3565 [ + + + + ]: 5230 : if (last_tsid == InvalidOid || last_tsid != cur_tsid)
3566 : : {
3567 : 9 : Size sz;
3568 : :
3569 : 9 : num_spaces++;
3570 : :
3571 : : /*
3572 : : * Not worth adding grow-by-power-of-2 logic here - even with a
3573 : : * few hundred tablespaces this should be fine.
3574 : : */
3575 : 9 : sz = sizeof(CkptTsStatus) * num_spaces;
3576 : :
3577 [ + + ]: 9 : if (per_ts_stat == NULL)
3578 : 5 : per_ts_stat = (CkptTsStatus *) palloc(sz);
3579 : : else
3580 : 4 : per_ts_stat = (CkptTsStatus *) repalloc(per_ts_stat, sz);
3581 : :
3582 : 9 : s = &per_ts_stat[num_spaces - 1];
3583 : 9 : memset(s, 0, sizeof(*s));
3584 : 9 : s->tsId = cur_tsid;
3585 : :
3586 : : /*
3587 : : * The first buffer in this tablespace. As CkptBufferIds is sorted
3588 : : * by tablespace all (s->num_to_scan) buffers in this tablespace
3589 : : * will follow afterwards.
3590 : : */
3591 : 9 : s->index = i;
3592 : :
3593 : : /*
3594 : : * progress_slice will be determined once we know how many buffers
3595 : : * are in each tablespace, i.e. after this loop.
3596 : : */
3597 : :
3598 : 9 : last_tsid = cur_tsid;
3599 : 9 : }
3600 : : else
3601 : : {
3602 : 5221 : s = &per_ts_stat[num_spaces - 1];
3603 : : }
3604 : :
3605 : 5230 : s->num_to_scan++;
3606 : :
3607 : : /* Check for barrier events. */
3608 [ + - ]: 5230 : if (ProcSignalBarrierPending)
3609 : 0 : ProcessProcSignalBarrier();
3610 : 5230 : }
3611 : :
3612 [ + - ]: 5 : Assert(num_spaces > 0);
3613 : :
3614 : : /*
3615 : : * Build a min-heap over the write-progress in the individual tablespaces,
3616 : : * and compute how large a portion of the total progress a single
3617 : : * processed buffer is.
3618 : : */
3619 : 5 : ts_heap = binaryheap_allocate(num_spaces,
3620 : : ts_ckpt_progress_comparator,
3621 : : NULL);
3622 : :
3623 [ + + ]: 14 : for (i = 0; i < num_spaces; i++)
3624 : : {
3625 : 9 : CkptTsStatus *ts_stat = &per_ts_stat[i];
3626 : :
3627 : 9 : ts_stat->progress_slice = (float8) num_to_scan / ts_stat->num_to_scan;
3628 : :
3629 : 9 : binaryheap_add_unordered(ts_heap, PointerGetDatum(ts_stat));
3630 : 9 : }
3631 : :
3632 : 5 : binaryheap_build(ts_heap);
3633 : :
3634 : : /*
3635 : : * Iterate through to-be-checkpointed buffers and write the ones (still)
3636 : : * marked with BM_CHECKPOINT_NEEDED. The writes are balanced between
3637 : : * tablespaces; otherwise the sorting would lead to only one tablespace
3638 : : * receiving writes at a time, making inefficient use of the hardware.
3639 : : */
3640 : 5 : num_processed = 0;
3641 : 5 : num_written = 0;
3642 [ + + ]: 5235 : while (!binaryheap_empty(ts_heap))
3643 : : {
3644 : 5230 : BufferDesc *bufHdr = NULL;
3645 : 10460 : CkptTsStatus *ts_stat = (CkptTsStatus *)
3646 : 5230 : DatumGetPointer(binaryheap_first(ts_heap));
3647 : :
3648 : 5230 : buf_id = CkptBufferIds[ts_stat->index].buf_id;
3649 [ + - ]: 5230 : Assert(buf_id != -1);
3650 : :
3651 : 5230 : bufHdr = GetBufferDescriptor(buf_id);
3652 : :
3653 : 5230 : num_processed++;
3654 : :
3655 : : /*
3656 : : * We don't need to acquire the lock here, because we're only looking
3657 : : * at a single bit. It's possible that someone else writes the buffer
3658 : : * and clears the flag right after we check, but that doesn't matter
3659 : : * since SyncOneBuffer will then do nothing. However, there is a
3660 : : * further race condition: it's conceivable that between the time we
3661 : : * examine the bit here and the time SyncOneBuffer acquires the lock,
3662 : : * someone else not only wrote the buffer but replaced it with another
3663 : : * page and dirtied it. In that improbable case, SyncOneBuffer will
3664 : : * write the buffer though we didn't need to. It doesn't seem worth
3665 : : * guarding against this, though.
3666 : : */
3667 [ - + ]: 5230 : if (pg_atomic_read_u64(&bufHdr->state) & BM_CHECKPOINT_NEEDED)
3668 : : {
3669 [ - + ]: 5230 : if (SyncOneBuffer(buf_id, false, &wb_context) & BUF_WRITTEN)
3670 : : {
3671 : 5230 : TRACE_POSTGRESQL_BUFFER_SYNC_WRITTEN(buf_id);
3672 : 5230 : PendingCheckpointerStats.buffers_written++;
3673 : 5230 : num_written++;
3674 : 5230 : }
3675 : 5230 : }
3676 : :
3677 : : /*
3678 : : * Measure progress independent of actually having to flush the buffer
3679 : : * - otherwise writing become unbalanced.
3680 : : */
3681 : 5230 : ts_stat->progress += ts_stat->progress_slice;
3682 : 5230 : ts_stat->num_scanned++;
3683 : 5230 : ts_stat->index++;
3684 : :
3685 : : /* Have all the buffers from the tablespace been processed? */
3686 [ + + ]: 5230 : if (ts_stat->num_scanned == ts_stat->num_to_scan)
3687 : : {
3688 : 9 : binaryheap_remove_first(ts_heap);
3689 : 9 : }
3690 : : else
3691 : : {
3692 : : /* update heap with the new progress */
3693 : 5221 : binaryheap_replace_first(ts_heap, PointerGetDatum(ts_stat));
3694 : : }
3695 : :
3696 : : /*
3697 : : * Sleep to throttle our I/O rate.
3698 : : *
3699 : : * (This will check for barrier events even if it doesn't sleep.)
3700 : : */
3701 : 5230 : CheckpointWriteDelay(flags, (double) num_processed / num_to_scan);
3702 : 5230 : }
3703 : :
3704 : : /*
3705 : : * Issue all pending flushes. Only checkpointer calls BufferSync(), so
3706 : : * IOContext will always be IOCONTEXT_NORMAL.
3707 : : */
3708 : 5 : IssuePendingWritebacks(&wb_context, IOCONTEXT_NORMAL);
3709 : :
3710 : 5 : pfree(per_ts_stat);
3711 : 5 : per_ts_stat = NULL;
3712 : 5 : binaryheap_free(ts_heap);
3713 : :
3714 : : /*
3715 : : * Update checkpoint statistics. As noted above, this doesn't include
3716 : : * buffers written by other backends or bgwriter scan.
3717 : : */
3718 : 5 : CheckpointStats.ckpt_bufs_written += num_written;
3719 : :
3720 : 5 : TRACE_POSTGRESQL_BUFFER_SYNC_DONE(NBuffers, num_written, num_to_scan);
3721 [ - + ]: 7 : }
3722 : :
3723 : : /*
3724 : : * BgBufferSync -- Write out some dirty buffers in the pool.
3725 : : *
3726 : : * This is called periodically by the background writer process.
3727 : : *
3728 : : * Returns true if it's appropriate for the bgwriter process to go into
3729 : : * low-power hibernation mode. (This happens if the strategy clock-sweep
3730 : : * has been "lapped" and no buffer allocations have occurred recently,
3731 : : * or if the bgwriter has been effectively disabled by setting
3732 : : * bgwriter_lru_maxpages to 0.)
3733 : : */
3734 : : bool
3735 : 24 : BgBufferSync(WritebackContext *wb_context)
3736 : : {
3737 : : /* info obtained from freelist.c */
3738 : 24 : int strategy_buf_id;
3739 : 24 : uint32 strategy_passes;
3740 : 24 : uint32 recent_alloc;
3741 : :
3742 : : /*
3743 : : * Information saved between calls so we can determine the strategy
3744 : : * point's advance rate and avoid scanning already-cleaned buffers.
3745 : : */
3746 : : static bool saved_info_valid = false;
3747 : : static int prev_strategy_buf_id;
3748 : : static uint32 prev_strategy_passes;
3749 : : static int next_to_clean;
3750 : : static uint32 next_passes;
3751 : :
3752 : : /* Moving averages of allocation rate and clean-buffer density */
3753 : : static float smoothed_alloc = 0;
3754 : : static float smoothed_density = 10.0;
3755 : :
3756 : : /* Potentially these could be tunables, but for now, not */
3757 : 24 : float smoothing_samples = 16;
3758 : 24 : float scan_whole_pool_milliseconds = 120000.0;
3759 : :
3760 : : /* Used to compute how far we scan ahead */
3761 : 24 : long strategy_delta;
3762 : 24 : int bufs_to_lap;
3763 : 24 : int bufs_ahead;
3764 : 24 : float scans_per_alloc;
3765 : 24 : int reusable_buffers_est;
3766 : 24 : int upcoming_alloc_est;
3767 : 24 : int min_scan_buffers;
3768 : :
3769 : : /* Variables for the scanning loop proper */
3770 : 24 : int num_to_scan;
3771 : 24 : int num_written;
3772 : 24 : int reusable_buffers;
3773 : :
3774 : : /* Variables for final smoothed_density update */
3775 : 24 : long new_strategy_delta;
3776 : 24 : uint32 new_recent_alloc;
3777 : :
3778 : : /*
3779 : : * Find out where the clock-sweep currently is, and how many buffer
3780 : : * allocations have happened since our last call.
3781 : : */
3782 : 24 : strategy_buf_id = StrategySyncStart(&strategy_passes, &recent_alloc);
3783 : :
3784 : : /* Report buffer alloc counts to pgstat */
3785 : 24 : PendingBgWriterStats.buf_alloc += recent_alloc;
3786 : :
3787 : : /*
3788 : : * If we're not running the LRU scan, just stop after doing the stats
3789 : : * stuff. We mark the saved state invalid so that we can recover sanely
3790 : : * if LRU scan is turned back on later.
3791 : : */
3792 [ - + ]: 24 : if (bgwriter_lru_maxpages <= 0)
3793 : : {
3794 : 0 : saved_info_valid = false;
3795 : 0 : return true;
3796 : : }
3797 : :
3798 : : /*
3799 : : * Compute strategy_delta = how many buffers have been scanned by the
3800 : : * clock-sweep since last time. If first time through, assume none. Then
3801 : : * see if we are still ahead of the clock-sweep, and if so, how many
3802 : : * buffers we could scan before we'd catch up with it and "lap" it. Note:
3803 : : * weird-looking coding of xxx_passes comparisons are to avoid bogus
3804 : : * behavior when the passes counts wrap around.
3805 : : */
3806 [ + + ]: 24 : if (saved_info_valid)
3807 : : {
3808 : 23 : int32 passes_delta = strategy_passes - prev_strategy_passes;
3809 : :
3810 : 23 : strategy_delta = strategy_buf_id - prev_strategy_buf_id;
3811 : 23 : strategy_delta += (long) passes_delta * NBuffers;
3812 : :
3813 [ + - ]: 23 : Assert(strategy_delta >= 0);
3814 : :
3815 [ + + ]: 23 : if ((int32) (next_passes - strategy_passes) > 0)
3816 : : {
3817 : : /* we're one pass ahead of the strategy point */
3818 : 17 : bufs_to_lap = strategy_buf_id - next_to_clean;
3819 : : #ifdef BGW_DEBUG
3820 : : elog(DEBUG2, "bgwriter ahead: bgw %u-%u strategy %u-%u delta=%ld lap=%d",
3821 : : next_passes, next_to_clean,
3822 : : strategy_passes, strategy_buf_id,
3823 : : strategy_delta, bufs_to_lap);
3824 : : #endif
3825 : 17 : }
3826 [ + - + + ]: 6 : else if (next_passes == strategy_passes &&
3827 : 6 : next_to_clean >= strategy_buf_id)
3828 : : {
3829 : : /* on same pass, but ahead or at least not behind */
3830 : 5 : bufs_to_lap = NBuffers - (next_to_clean - strategy_buf_id);
3831 : : #ifdef BGW_DEBUG
3832 : : elog(DEBUG2, "bgwriter ahead: bgw %u-%u strategy %u-%u delta=%ld lap=%d",
3833 : : next_passes, next_to_clean,
3834 : : strategy_passes, strategy_buf_id,
3835 : : strategy_delta, bufs_to_lap);
3836 : : #endif
3837 : 5 : }
3838 : : else
3839 : : {
3840 : : /*
3841 : : * We're behind, so skip forward to the strategy point and start
3842 : : * cleaning from there.
3843 : : */
3844 : : #ifdef BGW_DEBUG
3845 : : elog(DEBUG2, "bgwriter behind: bgw %u-%u strategy %u-%u delta=%ld",
3846 : : next_passes, next_to_clean,
3847 : : strategy_passes, strategy_buf_id,
3848 : : strategy_delta);
3849 : : #endif
3850 : 1 : next_to_clean = strategy_buf_id;
3851 : 1 : next_passes = strategy_passes;
3852 : 1 : bufs_to_lap = NBuffers;
3853 : : }
3854 : 23 : }
3855 : : else
3856 : : {
3857 : : /*
3858 : : * Initializing at startup or after LRU scanning had been off. Always
3859 : : * start at the strategy point.
3860 : : */
3861 : : #ifdef BGW_DEBUG
3862 : : elog(DEBUG2, "bgwriter initializing: strategy %u-%u",
3863 : : strategy_passes, strategy_buf_id);
3864 : : #endif
3865 : 1 : strategy_delta = 0;
3866 : 1 : next_to_clean = strategy_buf_id;
3867 : 1 : next_passes = strategy_passes;
3868 : 1 : bufs_to_lap = NBuffers;
3869 : : }
3870 : :
3871 : : /* Update saved info for next time */
3872 : 24 : prev_strategy_buf_id = strategy_buf_id;
3873 : 24 : prev_strategy_passes = strategy_passes;
3874 : 24 : saved_info_valid = true;
3875 : :
3876 : : /*
3877 : : * Compute how many buffers had to be scanned for each new allocation, ie,
3878 : : * 1/density of reusable buffers, and track a moving average of that.
3879 : : *
3880 : : * If the strategy point didn't move, we don't update the density estimate
3881 : : */
3882 [ + + - + ]: 24 : if (strategy_delta > 0 && recent_alloc > 0)
3883 : : {
3884 : 13 : scans_per_alloc = (float) strategy_delta / (float) recent_alloc;
3885 : 26 : smoothed_density += (scans_per_alloc - smoothed_density) /
3886 : 13 : smoothing_samples;
3887 : 13 : }
3888 : :
3889 : : /*
3890 : : * Estimate how many reusable buffers there are between the current
3891 : : * strategy point and where we've scanned ahead to, based on the smoothed
3892 : : * density estimate.
3893 : : */
3894 : 24 : bufs_ahead = NBuffers - bufs_to_lap;
3895 : 24 : reusable_buffers_est = (float) bufs_ahead / smoothed_density;
3896 : :
3897 : : /*
3898 : : * Track a moving average of recent buffer allocations. Here, rather than
3899 : : * a true average we want a fast-attack, slow-decline behavior: we
3900 : : * immediately follow any increase.
3901 : : */
3902 [ + + ]: 24 : if (smoothed_alloc <= (float) recent_alloc)
3903 : 3 : smoothed_alloc = recent_alloc;
3904 : : else
3905 : 42 : smoothed_alloc += ((float) recent_alloc - smoothed_alloc) /
3906 : 21 : smoothing_samples;
3907 : :
3908 : : /* Scale the estimate by a GUC to allow more aggressive tuning. */
3909 : 24 : upcoming_alloc_est = (int) (smoothed_alloc * bgwriter_lru_multiplier);
3910 : :
3911 : : /*
3912 : : * If recent_alloc remains at zero for many cycles, smoothed_alloc will
3913 : : * eventually underflow to zero, and the underflows produce annoying
3914 : : * kernel warnings on some platforms. Once upcoming_alloc_est has gone to
3915 : : * zero, there's no point in tracking smaller and smaller values of
3916 : : * smoothed_alloc, so just reset it to exactly zero to avoid this
3917 : : * syndrome. It will pop back up as soon as recent_alloc increases.
3918 : : */
3919 [ + + ]: 24 : if (upcoming_alloc_est == 0)
3920 : 2 : smoothed_alloc = 0;
3921 : :
3922 : : /*
3923 : : * Even in cases where there's been little or no buffer allocation
3924 : : * activity, we want to make a small amount of progress through the buffer
3925 : : * cache so that as many reusable buffers as possible are clean after an
3926 : : * idle period.
3927 : : *
3928 : : * (scan_whole_pool_milliseconds / BgWriterDelay) computes how many times
3929 : : * the BGW will be called during the scan_whole_pool time; slice the
3930 : : * buffer pool into that many sections.
3931 : : */
3932 : 24 : min_scan_buffers = (int) (NBuffers / (scan_whole_pool_milliseconds / BgWriterDelay));
3933 : :
3934 [ + + ]: 24 : if (upcoming_alloc_est < (min_scan_buffers + reusable_buffers_est))
3935 : : {
3936 : : #ifdef BGW_DEBUG
3937 : : elog(DEBUG2, "bgwriter: alloc_est=%d too small, using min=%d + reusable_est=%d",
3938 : : upcoming_alloc_est, min_scan_buffers, reusable_buffers_est);
3939 : : #endif
3940 : 17 : upcoming_alloc_est = min_scan_buffers + reusable_buffers_est;
3941 : 17 : }
3942 : :
3943 : : /*
3944 : : * Now write out dirty reusable buffers, working forward from the
3945 : : * next_to_clean point, until we have lapped the strategy scan, or cleaned
3946 : : * enough buffers to match our estimate of the next cycle's allocation
3947 : : * requirements, or hit the bgwriter_lru_maxpages limit.
3948 : : */
3949 : :
3950 : 24 : num_to_scan = bufs_to_lap;
3951 : 24 : num_written = 0;
3952 : 24 : reusable_buffers = reusable_buffers_est;
3953 : :
3954 : : /* Execute the LRU scan */
3955 [ + + + + ]: 19373 : while (num_to_scan > 0 && reusable_buffers < upcoming_alloc_est)
3956 : : {
3957 : 38698 : int sync_state = SyncOneBuffer(next_to_clean, true,
3958 : 19349 : wb_context);
3959 : :
3960 [ + + ]: 19349 : if (++next_to_clean >= NBuffers)
3961 : : {
3962 : 1 : next_to_clean = 0;
3963 : 1 : next_passes++;
3964 : 1 : }
3965 : 19349 : num_to_scan--;
3966 : :
3967 [ - + ]: 19349 : if (sync_state & BUF_WRITTEN)
3968 : : {
3969 : 0 : reusable_buffers++;
3970 [ # # ]: 0 : if (++num_written >= bgwriter_lru_maxpages)
3971 : : {
3972 : 0 : PendingBgWriterStats.maxwritten_clean++;
3973 : 0 : break;
3974 : : }
3975 : 0 : }
3976 [ + + ]: 19349 : else if (sync_state & BUF_REUSABLE)
3977 : 14161 : reusable_buffers++;
3978 [ - - + ]: 19349 : }
3979 : :
3980 : 24 : PendingBgWriterStats.buf_written_clean += num_written;
3981 : :
3982 : : #ifdef BGW_DEBUG
3983 : : elog(DEBUG1, "bgwriter: recent_alloc=%u smoothed=%.2f delta=%ld ahead=%d density=%.2f reusable_est=%d upcoming_est=%d scanned=%d wrote=%d reusable=%d",
3984 : : recent_alloc, smoothed_alloc, strategy_delta, bufs_ahead,
3985 : : smoothed_density, reusable_buffers_est, upcoming_alloc_est,
3986 : : bufs_to_lap - num_to_scan,
3987 : : num_written,
3988 : : reusable_buffers - reusable_buffers_est);
3989 : : #endif
3990 : :
3991 : : /*
3992 : : * Consider the above scan as being like a new allocation scan.
3993 : : * Characterize its density and update the smoothed one based on it. This
3994 : : * effectively halves the moving average period in cases where both the
3995 : : * strategy and the background writer are doing some useful scanning,
3996 : : * which is helpful because a long memory isn't as desirable on the
3997 : : * density estimates.
3998 : : */
3999 : 24 : new_strategy_delta = bufs_to_lap - num_to_scan;
4000 : 24 : new_recent_alloc = reusable_buffers - reusable_buffers_est;
4001 [ + + + + ]: 24 : if (new_strategy_delta > 0 && new_recent_alloc > 0)
4002 : : {
4003 : 7 : scans_per_alloc = (float) new_strategy_delta / (float) new_recent_alloc;
4004 : 14 : smoothed_density += (scans_per_alloc - smoothed_density) /
4005 : 7 : smoothing_samples;
4006 : :
4007 : : #ifdef BGW_DEBUG
4008 : : elog(DEBUG2, "bgwriter: cleaner density alloc=%u scan=%ld density=%.2f new smoothed=%.2f",
4009 : : new_recent_alloc, new_strategy_delta,
4010 : : scans_per_alloc, smoothed_density);
4011 : : #endif
4012 : 7 : }
4013 : :
4014 : : /* Return true if OK to hibernate */
4015 [ + + ]: 24 : return (bufs_to_lap == 0 && recent_alloc == 0);
4016 : 24 : }
4017 : :
4018 : : /*
4019 : : * SyncOneBuffer -- process a single buffer during syncing.
4020 : : *
4021 : : * If skip_recently_used is true, we don't write currently-pinned buffers, nor
4022 : : * buffers marked recently used, as these are not replacement candidates.
4023 : : *
4024 : : * Returns a bitmask containing the following flag bits:
4025 : : * BUF_WRITTEN: we wrote the buffer.
4026 : : * BUF_REUSABLE: buffer is available for replacement, ie, it has
4027 : : * pin count 0 and usage count 0.
4028 : : *
4029 : : * (BUF_WRITTEN could be set in error if FlushBuffer finds the buffer clean
4030 : : * after locking it, but we don't care all that much.)
4031 : : */
4032 : : static int
4033 : 24579 : SyncOneBuffer(int buf_id, bool skip_recently_used, WritebackContext *wb_context)
4034 : : {
4035 : 24579 : BufferDesc *bufHdr = GetBufferDescriptor(buf_id);
4036 : 24579 : int result = 0;
4037 : 24579 : uint64 buf_state;
4038 : 24579 : BufferTag tag;
4039 : :
4040 : : /* Make sure we can handle the pin */
4041 : 24579 : ReservePrivateRefCountEntry();
4042 : 24579 : ResourceOwnerEnlarge(CurrentResourceOwner);
4043 : :
4044 : : /*
4045 : : * Check whether buffer needs writing.
4046 : : *
4047 : : * We can make this check without taking the buffer content lock so long
4048 : : * as we mark pages dirty in access methods *before* logging changes with
4049 : : * XLogInsert(): if someone marks the buffer dirty just after our check we
4050 : : * don't worry because our checkpoint.redo points before log record for
4051 : : * upcoming changes and so we are not required to write such dirty buffer.
4052 : : */
4053 : 24579 : buf_state = LockBufHdr(bufHdr);
4054 : :
4055 [ + + + + ]: 24579 : if (BUF_STATE_GET_REFCOUNT(buf_state) == 0 &&
4056 : 24569 : BUF_STATE_GET_USAGECOUNT(buf_state) == 0)
4057 : : {
4058 : 14161 : result |= BUF_REUSABLE;
4059 : 14161 : }
4060 [ + + ]: 10418 : else if (skip_recently_used)
4061 : : {
4062 : : /* Caller told us not to write recently-used buffers */
4063 : 5188 : UnlockBufHdr(bufHdr);
4064 : 5188 : return result;
4065 : : }
4066 : :
4067 [ + + - + ]: 19391 : if (!(buf_state & BM_VALID) || !(buf_state & BM_DIRTY))
4068 : : {
4069 : : /* It's clean, so nothing to do */
4070 : 14161 : UnlockBufHdr(bufHdr);
4071 : 14161 : return result;
4072 : : }
4073 : :
4074 : : /*
4075 : : * Pin it, share-lock it, write it. (FlushBuffer will do nothing if the
4076 : : * buffer is clean by the time we've locked it.)
4077 : : */
4078 : 5230 : PinBuffer_Locked(bufHdr);
4079 : :
4080 : 5230 : FlushUnlockedBuffer(bufHdr, NULL, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
4081 : :
4082 : 5230 : tag = bufHdr->tag;
4083 : :
4084 : 5230 : UnpinBuffer(bufHdr);
4085 : :
4086 : : /*
4087 : : * SyncOneBuffer() is only called by checkpointer and bgwriter, so
4088 : : * IOContext will always be IOCONTEXT_NORMAL.
4089 : : */
4090 : 5230 : ScheduleBufferTagForWriteback(wb_context, IOCONTEXT_NORMAL, &tag);
4091 : :
4092 : 5230 : return result | BUF_WRITTEN;
4093 : 24579 : }
4094 : :
4095 : : /*
4096 : : * AtEOXact_Buffers - clean up at end of transaction.
4097 : : *
4098 : : * As of PostgreSQL 8.0, buffer pins should get released by the
4099 : : * ResourceOwner mechanism. This routine is just a debugging
4100 : : * cross-check that no pins remain.
4101 : : */
4102 : : void
4103 : 57914 : AtEOXact_Buffers(bool isCommit)
4104 : : {
4105 : 57914 : CheckForBufferLeaks();
4106 : :
4107 : 57914 : AtEOXact_LocalBuffers(isCommit);
4108 : :
4109 [ + - ]: 57914 : Assert(PrivateRefCountOverflowed == 0);
4110 : 57914 : }
4111 : :
4112 : : /*
4113 : : * Initialize access to shared buffer pool
4114 : : *
4115 : : * This is called during backend startup (whether standalone or under the
4116 : : * postmaster). It sets up for this backend's access to the already-existing
4117 : : * buffer pool.
4118 : : */
4119 : : void
4120 : 806 : InitBufferManagerAccess(void)
4121 : : {
4122 : 806 : HASHCTL hash_ctl;
4123 : :
4124 : : /*
4125 : : * An advisory limit on the number of pins each backend should hold, based
4126 : : * on shared_buffers and the maximum number of connections possible.
4127 : : * That's very pessimistic, but outside toy-sized shared_buffers it should
4128 : : * allow plenty of pins. LimitAdditionalPins() and
4129 : : * GetAdditionalPinLimit() can be used to check the remaining balance.
4130 : : */
4131 : 806 : MaxProportionalPins = NBuffers / (MaxBackends + NUM_AUXILIARY_PROCS);
4132 : :
4133 : 806 : memset(&PrivateRefCountArray, 0, sizeof(PrivateRefCountArray));
4134 : 806 : memset(&PrivateRefCountArrayKeys, 0, sizeof(PrivateRefCountArrayKeys));
4135 : :
4136 : 806 : hash_ctl.keysize = sizeof(Buffer);
4137 : 806 : hash_ctl.entrysize = sizeof(PrivateRefCountEntry);
4138 : :
4139 : 806 : PrivateRefCountHash = hash_create("PrivateRefCount", 100, &hash_ctl,
4140 : : HASH_ELEM | HASH_BLOBS);
4141 : :
4142 : : /*
4143 : : * AtProcExit_Buffers needs LWLock access, and thereby has to be called at
4144 : : * the corresponding phase of backend shutdown.
4145 : : */
4146 [ + - ]: 806 : Assert(MyProc != NULL);
4147 : 806 : on_shmem_exit(AtProcExit_Buffers, 0);
4148 : 806 : }
4149 : :
4150 : : /*
4151 : : * During backend exit, ensure that we released all shared-buffer locks and
4152 : : * assert that we have no remaining pins.
4153 : : */
4154 : : static void
4155 : 806 : AtProcExit_Buffers(int code, Datum arg)
4156 : : {
4157 : 806 : UnlockBuffers();
4158 : :
4159 : 806 : CheckForBufferLeaks();
4160 : :
4161 : : /* localbuf.c needs a chance too */
4162 : 806 : AtProcExit_LocalBuffers();
4163 : 806 : }
4164 : :
4165 : : /*
4166 : : * CheckForBufferLeaks - ensure this backend holds no buffer pins
4167 : : *
4168 : : * As of PostgreSQL 8.0, buffer pins should get released by the
4169 : : * ResourceOwner mechanism. This routine is just a debugging
4170 : : * cross-check that no pins remain.
4171 : : */
4172 : : static void
4173 : 58720 : CheckForBufferLeaks(void)
4174 : : {
4175 : : #ifdef USE_ASSERT_CHECKING
4176 : 58720 : int RefCountErrors = 0;
4177 : 58720 : PrivateRefCountEntry *res;
4178 : 58720 : int i;
4179 : 58720 : char *s;
4180 : :
4181 : : /* check the array */
4182 [ + + ]: 528480 : for (i = 0; i < REFCOUNT_ARRAY_ENTRIES; i++)
4183 : : {
4184 [ + - ]: 469760 : if (PrivateRefCountArrayKeys[i] != InvalidBuffer)
4185 : : {
4186 : 0 : res = &PrivateRefCountArray[i];
4187 : :
4188 : 0 : s = DebugPrintBufferRefcount(res->buffer);
4189 [ # # # # ]: 0 : elog(WARNING, "buffer refcount leak: %s", s);
4190 : 0 : pfree(s);
4191 : :
4192 : 0 : RefCountErrors++;
4193 : 0 : }
4194 : 469760 : }
4195 : :
4196 : : /* if necessary search the hash */
4197 [ + - ]: 58720 : if (PrivateRefCountOverflowed)
4198 : : {
4199 : 0 : HASH_SEQ_STATUS hstat;
4200 : :
4201 : 0 : hash_seq_init(&hstat, PrivateRefCountHash);
4202 [ # # ]: 0 : while ((res = (PrivateRefCountEntry *) hash_seq_search(&hstat)) != NULL)
4203 : : {
4204 : 0 : s = DebugPrintBufferRefcount(res->buffer);
4205 [ # # # # ]: 0 : elog(WARNING, "buffer refcount leak: %s", s);
4206 : 0 : pfree(s);
4207 : 0 : RefCountErrors++;
4208 : : }
4209 : 0 : }
4210 : :
4211 [ + - ]: 58720 : Assert(RefCountErrors == 0);
4212 : : #endif
4213 : 58720 : }
4214 : :
4215 : : #ifdef USE_ASSERT_CHECKING
4216 : : /*
4217 : : * Check for exclusive-locked catalog buffers. This is the core of
4218 : : * AssertCouldGetRelation().
4219 : : *
4220 : : * A backend would self-deadlock on the content lock if the catalog scan read
4221 : : * the exclusive-locked buffer. The main threat is exclusive-locked buffers
4222 : : * of catalogs used in relcache, because a catcache search on any catalog may
4223 : : * build that catalog's relcache entry. We don't have an inventory of
4224 : : * catalogs relcache uses, so just check buffers of most catalogs.
4225 : : *
4226 : : * It's better to minimize waits while holding an exclusive buffer lock, so it
4227 : : * would be nice to broaden this check not to be catalog-specific. However,
4228 : : * bttextcmp() accesses pg_collation, and non-core opclasses might similarly
4229 : : * read tables. That is deadlock-free as long as there's no loop in the
4230 : : * dependency graph: modifying table A may cause an opclass to read table B,
4231 : : * but it must not cause a read of table A.
4232 : : */
4233 : : void
4234 : 19867411 : AssertBufferLocksPermitCatalogRead(void)
4235 : : {
4236 : 19867411 : PrivateRefCountEntry *res;
4237 : :
4238 : : /* check the array */
4239 [ + + ]: 178806699 : for (int i = 0; i < REFCOUNT_ARRAY_ENTRIES; i++)
4240 : : {
4241 [ + + ]: 158939288 : if (PrivateRefCountArrayKeys[i] != InvalidBuffer)
4242 : : {
4243 : 8081887 : res = &PrivateRefCountArray[i];
4244 : :
4245 [ + - ]: 8081887 : if (res->buffer == InvalidBuffer)
4246 : 0 : continue;
4247 : :
4248 : 8081887 : AssertNotCatalogBufferLock(res->buffer, res->data.lockmode);
4249 : 8081887 : }
4250 : 158939288 : }
4251 : :
4252 : : /* if necessary search the hash */
4253 [ + + ]: 19867411 : if (PrivateRefCountOverflowed)
4254 : : {
4255 : 2316 : HASH_SEQ_STATUS hstat;
4256 : :
4257 : 2316 : hash_seq_init(&hstat, PrivateRefCountHash);
4258 [ + + ]: 5575 : while ((res = (PrivateRefCountEntry *) hash_seq_search(&hstat)) != NULL)
4259 : : {
4260 : 3259 : AssertNotCatalogBufferLock(res->buffer, res->data.lockmode);
4261 : : }
4262 : 2316 : }
4263 : 19867411 : }
4264 : :
4265 : : static void
4266 : 8085146 : AssertNotCatalogBufferLock(Buffer buffer, BufferLockMode mode)
4267 : : {
4268 : 8085146 : BufferDesc *bufHdr = GetBufferDescriptor(buffer - 1);
4269 : 8085146 : BufferTag tag;
4270 : 8085146 : Oid relid;
4271 : :
4272 [ + + ]: 8085146 : if (mode != BUFFER_LOCK_EXCLUSIVE)
4273 : 8084031 : return;
4274 : :
4275 : 1115 : tag = bufHdr->tag;
4276 : :
4277 : : /*
4278 : : * This relNumber==relid assumption holds until a catalog experiences
4279 : : * VACUUM FULL or similar. After a command like that, relNumber will be
4280 : : * in the normal (non-catalog) range, and we lose the ability to detect
4281 : : * hazardous access to that catalog. Calling RelidByRelfilenumber() would
4282 : : * close that gap, but RelidByRelfilenumber() might then deadlock with a
4283 : : * held lock.
4284 : : */
4285 : 1115 : relid = tag.relNumber;
4286 : :
4287 [ - + ]: 1115 : if (IsCatalogTextUniqueIndexOid(relid)) /* see comments at the callee */
4288 : 0 : return;
4289 : :
4290 [ + - ]: 1115 : Assert(!IsCatalogRelationOid(relid));
4291 [ - + ]: 8085146 : }
4292 : : #endif
4293 : :
4294 : :
4295 : : /*
4296 : : * Helper routine to issue warnings when a buffer is unexpectedly pinned
4297 : : */
4298 : : char *
4299 : 0 : DebugPrintBufferRefcount(Buffer buffer)
4300 : : {
4301 : 0 : BufferDesc *buf;
4302 : 0 : int32 loccount;
4303 : 0 : char *result;
4304 : 0 : ProcNumber backend;
4305 : 0 : uint64 buf_state;
4306 : :
4307 [ # # ]: 0 : Assert(BufferIsValid(buffer));
4308 [ # # ]: 0 : if (BufferIsLocal(buffer))
4309 : : {
4310 : 0 : buf = GetLocalBufferDescriptor(-buffer - 1);
4311 : 0 : loccount = LocalRefCount[-buffer - 1];
4312 : 0 : backend = MyProcNumber;
4313 : 0 : }
4314 : : else
4315 : : {
4316 : 0 : buf = GetBufferDescriptor(buffer - 1);
4317 : 0 : loccount = GetPrivateRefCount(buffer);
4318 : 0 : backend = INVALID_PROC_NUMBER;
4319 : : }
4320 : :
4321 : : /* theoretically we should lock the bufHdr here */
4322 : 0 : buf_state = pg_atomic_read_u64(&buf->state);
4323 : :
4324 : 0 : result = psprintf("[%03d] (rel=%s, blockNum=%u, flags=0x%" PRIx64 ", refcount=%u %d)",
4325 : 0 : buffer,
4326 : 0 : relpathbackend(BufTagGetRelFileLocator(&buf->tag), backend,
4327 : 0 : BufTagGetForkNum(&buf->tag)).str,
4328 : 0 : buf->tag.blockNum, buf_state & BUF_FLAG_MASK,
4329 : 0 : BUF_STATE_GET_REFCOUNT(buf_state), loccount);
4330 : 0 : return result;
4331 : 0 : }
4332 : :
4333 : : /*
4334 : : * CheckPointBuffers
4335 : : *
4336 : : * Flush all dirty blocks in buffer pool to disk at checkpoint time.
4337 : : *
4338 : : * Note: temporary relations do not participate in checkpoints, so they don't
4339 : : * need to be flushed.
4340 : : */
4341 : : void
4342 : 7 : CheckPointBuffers(int flags)
4343 : : {
4344 : 7 : BufferSync(flags);
4345 : 7 : }
4346 : :
4347 : : /*
4348 : : * BufferGetBlockNumber
4349 : : * Returns the block number associated with a buffer.
4350 : : *
4351 : : * Note:
4352 : : * Assumes that the buffer is valid and pinned, else the
4353 : : * value may be obsolete immediately...
4354 : : */
4355 : : BlockNumber
4356 : 28623221 : BufferGetBlockNumber(Buffer buffer)
4357 : : {
4358 : 28623221 : BufferDesc *bufHdr;
4359 : :
4360 [ - + # # : 28623221 : Assert(BufferIsPinned(buffer));
+ + ]
4361 : :
4362 [ + + ]: 28623221 : if (BufferIsLocal(buffer))
4363 : 1013794 : bufHdr = GetLocalBufferDescriptor(-buffer - 1);
4364 : : else
4365 : 27609427 : bufHdr = GetBufferDescriptor(buffer - 1);
4366 : :
4367 : : /* pinned, so OK to read tag without spinlock */
4368 : 57246442 : return bufHdr->tag.blockNum;
4369 : 28623221 : }
4370 : :
4371 : : /*
4372 : : * BufferGetTag
4373 : : * Returns the relfilelocator, fork number and block number associated with
4374 : : * a buffer.
4375 : : */
4376 : : void
4377 : 2595855 : BufferGetTag(Buffer buffer, RelFileLocator *rlocator, ForkNumber *forknum,
4378 : : BlockNumber *blknum)
4379 : : {
4380 : 2595855 : BufferDesc *bufHdr;
4381 : :
4382 : : /* Do the same checks as BufferGetBlockNumber. */
4383 [ - + # # : 2595855 : Assert(BufferIsPinned(buffer));
- + ]
4384 : :
4385 [ + - ]: 2595855 : if (BufferIsLocal(buffer))
4386 : 0 : bufHdr = GetLocalBufferDescriptor(-buffer - 1);
4387 : : else
4388 : 2595855 : bufHdr = GetBufferDescriptor(buffer - 1);
4389 : :
4390 : : /* pinned, so OK to read tag without spinlock */
4391 : 2595855 : *rlocator = BufTagGetRelFileLocator(&bufHdr->tag);
4392 : 2595855 : *forknum = BufTagGetForkNum(&bufHdr->tag);
4393 : 2595855 : *blknum = bufHdr->tag.blockNum;
4394 : 2595855 : }
4395 : :
4396 : : /*
4397 : : * FlushBuffer
4398 : : * Physically write out a shared buffer.
4399 : : *
4400 : : * NOTE: this actually just passes the buffer contents to the kernel; the
4401 : : * real write to disk won't happen until the kernel feels like it. This
4402 : : * is okay from our point of view since we can redo the changes from WAL.
4403 : : * However, we will need to force the changes to disk via fsync before
4404 : : * we can checkpoint WAL.
4405 : : *
4406 : : * The caller must hold a pin on the buffer and have share-locked the
4407 : : * buffer contents. (Note: a share-lock does not prevent updates of
4408 : : * hint bits in the buffer, so the page could change while the write
4409 : : * is in progress, but we assume that that will not invalidate the data
4410 : : * written.)
4411 : : *
4412 : : * If the caller has an smgr reference for the buffer's relation, pass it
4413 : : * as the second parameter. If not, pass NULL.
4414 : : */
4415 : : static void
4416 : 6998 : FlushBuffer(BufferDesc *buf, SMgrRelation reln, IOObject io_object,
4417 : : IOContext io_context)
4418 : : {
4419 : 6998 : XLogRecPtr recptr;
4420 : 6998 : ErrorContextCallback errcallback;
4421 : 6998 : instr_time io_start;
4422 : 6998 : Block bufBlock;
4423 : 6998 : char *bufToWrite;
4424 : 6998 : uint64 buf_state;
4425 : :
4426 : : /*
4427 : : * Try to start an I/O operation. If StartBufferIO returns false, then
4428 : : * someone else flushed the buffer before we could, so we need not do
4429 : : * anything.
4430 : : */
4431 [ + - ]: 6998 : if (!StartBufferIO(buf, false, false))
4432 : 0 : return;
4433 : :
4434 : : /* Setup error traceback support for ereport() */
4435 : 6998 : errcallback.callback = shared_buffer_write_error_callback;
4436 : 6998 : errcallback.arg = buf;
4437 : 6998 : errcallback.previous = error_context_stack;
4438 : 6998 : error_context_stack = &errcallback;
4439 : :
4440 : : /* Find smgr relation for buffer */
4441 [ + + ]: 6998 : if (reln == NULL)
4442 : 5230 : reln = smgropen(BufTagGetRelFileLocator(&buf->tag), INVALID_PROC_NUMBER);
4443 : :
4444 : 6998 : TRACE_POSTGRESQL_BUFFER_FLUSH_START(BufTagGetForkNum(&buf->tag),
4445 : : buf->tag.blockNum,
4446 : : reln->smgr_rlocator.locator.spcOid,
4447 : : reln->smgr_rlocator.locator.dbOid,
4448 : : reln->smgr_rlocator.locator.relNumber);
4449 : :
4450 : 6998 : buf_state = LockBufHdr(buf);
4451 : :
4452 : : /*
4453 : : * Run PageGetLSN while holding header lock, since we don't have the
4454 : : * buffer locked exclusively in all cases.
4455 : : */
4456 : 6998 : recptr = BufferGetLSN(buf);
4457 : :
4458 : : /* To check if block content changes while flushing. - vadim 01/17/97 */
4459 : 6998 : UnlockBufHdrExt(buf, buf_state,
4460 : : 0, BM_JUST_DIRTIED,
4461 : : 0);
4462 : :
4463 : : /*
4464 : : * Force XLOG flush up to buffer's LSN. This implements the basic WAL
4465 : : * rule that log updates must hit disk before any of the data-file changes
4466 : : * they describe do.
4467 : : *
4468 : : * However, this rule does not apply to unlogged relations, which will be
4469 : : * lost after a crash anyway. Most unlogged relation pages do not bear
4470 : : * LSNs since we never emit WAL records for them, and therefore flushing
4471 : : * up through the buffer LSN would be useless, but harmless. However,
4472 : : * GiST indexes use LSNs internally to track page-splits, and therefore
4473 : : * unlogged GiST pages bear "fake" LSNs generated by
4474 : : * GetFakeLSNForUnloggedRel. It is unlikely but possible that the fake
4475 : : * LSN counter could advance past the WAL insertion point; and if it did
4476 : : * happen, attempting to flush WAL through that location would fail, with
4477 : : * disastrous system-wide consequences. To make sure that can't happen,
4478 : : * skip the flush if the buffer isn't permanent.
4479 : : */
4480 [ + + ]: 6998 : if (buf_state & BM_PERMANENT)
4481 : 6983 : XLogFlush(recptr);
4482 : :
4483 : : /*
4484 : : * Now it's safe to write the buffer to disk. Note that no one else should
4485 : : * have been able to write it, while we were busy with log flushing,
4486 : : * because we got the exclusive right to perform I/O by setting the
4487 : : * BM_IO_IN_PROGRESS bit.
4488 : : */
4489 : 6998 : bufBlock = BufHdrGetBlock(buf);
4490 : :
4491 : : /*
4492 : : * Update page checksum if desired. Since we have only shared lock on the
4493 : : * buffer, other processes might be updating hint bits in it, so we must
4494 : : * copy the page to private storage if we do checksumming.
4495 : : */
4496 : 6998 : bufToWrite = PageSetChecksumCopy((Page) bufBlock, buf->tag.blockNum);
4497 : :
4498 : 6998 : io_start = pgstat_prepare_io_time(track_io_timing);
4499 : :
4500 : : /*
4501 : : * bufToWrite is either the shared buffer or a copy, as appropriate.
4502 : : */
4503 : 13996 : smgrwrite(reln,
4504 : 6998 : BufTagGetForkNum(&buf->tag),
4505 : 6998 : buf->tag.blockNum,
4506 : 6998 : bufToWrite,
4507 : : false);
4508 : :
4509 : : /*
4510 : : * When a strategy is in use, only flushes of dirty buffers already in the
4511 : : * strategy ring are counted as strategy writes (IOCONTEXT
4512 : : * [BULKREAD|BULKWRITE|VACUUM] IOOP_WRITE) for the purpose of IO
4513 : : * statistics tracking.
4514 : : *
4515 : : * If a shared buffer initially added to the ring must be flushed before
4516 : : * being used, this is counted as an IOCONTEXT_NORMAL IOOP_WRITE.
4517 : : *
4518 : : * If a shared buffer which was added to the ring later because the
4519 : : * current strategy buffer is pinned or in use or because all strategy
4520 : : * buffers were dirty and rejected (for BAS_BULKREAD operations only)
4521 : : * requires flushing, this is counted as an IOCONTEXT_NORMAL IOOP_WRITE
4522 : : * (from_ring will be false).
4523 : : *
4524 : : * When a strategy is not in use, the write can only be a "regular" write
4525 : : * of a dirty shared buffer (IOCONTEXT_NORMAL IOOP_WRITE).
4526 : : */
4527 : 6998 : pgstat_count_io_op_time(IOOBJECT_RELATION, io_context,
4528 : : IOOP_WRITE, io_start, 1, BLCKSZ);
4529 : :
4530 : 6998 : pgBufferUsage.shared_blks_written++;
4531 : :
4532 : : /*
4533 : : * Mark the buffer as clean (unless BM_JUST_DIRTIED has become set) and
4534 : : * end the BM_IO_IN_PROGRESS state.
4535 : : */
4536 : 6998 : TerminateBufferIO(buf, true, 0, true, false);
4537 : :
4538 : 6998 : TRACE_POSTGRESQL_BUFFER_FLUSH_DONE(BufTagGetForkNum(&buf->tag),
4539 : : buf->tag.blockNum,
4540 : : reln->smgr_rlocator.locator.spcOid,
4541 : : reln->smgr_rlocator.locator.dbOid,
4542 : : reln->smgr_rlocator.locator.relNumber);
4543 : :
4544 : : /* Pop the error context stack */
4545 : 6998 : error_context_stack = errcallback.previous;
4546 [ - + ]: 6998 : }
4547 : :
4548 : : /*
4549 : : * Convenience wrapper around FlushBuffer() that locks/unlocks the buffer
4550 : : * before/after calling FlushBuffer().
4551 : : */
4552 : : static void
4553 : 6998 : FlushUnlockedBuffer(BufferDesc *buf, SMgrRelation reln,
4554 : : IOObject io_object, IOContext io_context)
4555 : : {
4556 : 6998 : Buffer buffer = BufferDescriptorGetBuffer(buf);
4557 : :
4558 : 6998 : BufferLockAcquire(buffer, buf, BUFFER_LOCK_SHARE);
4559 : 6998 : FlushBuffer(buf, reln, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
4560 : 6998 : BufferLockUnlock(buffer, buf);
4561 : 6998 : }
4562 : :
4563 : : /*
4564 : : * RelationGetNumberOfBlocksInFork
4565 : : * Determines the current number of pages in the specified relation fork.
4566 : : *
4567 : : * Note that the accuracy of the result will depend on the details of the
4568 : : * relation's storage. For builtin AMs it'll be accurate, but for external AMs
4569 : : * it might not be.
4570 : : */
4571 : : BlockNumber
4572 : 488167 : RelationGetNumberOfBlocksInFork(Relation relation, ForkNumber forkNum)
4573 : : {
4574 [ + + + + : 488167 : if (RELKIND_HAS_TABLE_AM(relation->rd_rel->relkind))
+ + ]
4575 : : {
4576 : : /*
4577 : : * Not every table AM uses BLCKSZ wide fixed size blocks. Therefore
4578 : : * tableam returns the size in bytes - but for the purpose of this
4579 : : * routine, we want the number of blocks. Therefore divide, rounding
4580 : : * up.
4581 : : */
4582 : 405814 : uint64 szbytes;
4583 : :
4584 : 405814 : szbytes = table_relation_size(relation, forkNum);
4585 : :
4586 : 405814 : return (szbytes + (BLCKSZ - 1)) / BLCKSZ;
4587 : 405814 : }
4588 [ + - + + : 82353 : else if (RELKIND_HAS_STORAGE(relation->rd_rel->relkind))
- + # # #
# ]
4589 : : {
4590 : 82353 : return smgrnblocks(RelationGetSmgr(relation), forkNum);
4591 : : }
4592 : : else
4593 : 0 : Assert(false);
4594 : :
4595 : 0 : return 0; /* keep compiler quiet */
4596 : 488167 : }
4597 : :
4598 : : /*
4599 : : * BufferIsPermanent
4600 : : * Determines whether a buffer will potentially still be around after
4601 : : * a crash. Caller must hold a buffer pin.
4602 : : */
4603 : : bool
4604 : 2011239 : BufferIsPermanent(Buffer buffer)
4605 : : {
4606 : 2011239 : BufferDesc *bufHdr;
4607 : :
4608 : : /* Local buffers are used only for temp relations. */
4609 [ + + ]: 2011239 : if (BufferIsLocal(buffer))
4610 : 194899 : return false;
4611 : :
4612 : : /* Make sure we've got a real buffer, and that we hold a pin on it. */
4613 [ + - ]: 1816340 : Assert(BufferIsValid(buffer));
4614 [ - + # # : 1816340 : Assert(BufferIsPinned(buffer));
- + ]
4615 : :
4616 : : /*
4617 : : * BM_PERMANENT can't be changed while we hold a pin on the buffer, so we
4618 : : * need not bother with the buffer header spinlock. Even if someone else
4619 : : * changes the buffer header state while we're doing this, the state is
4620 : : * changed atomically, so we'll read the old value or the new value, but
4621 : : * not random garbage.
4622 : : */
4623 : 1816340 : bufHdr = GetBufferDescriptor(buffer - 1);
4624 : 1816340 : return (pg_atomic_read_u64(&bufHdr->state) & BM_PERMANENT) != 0;
4625 : 2011239 : }
4626 : :
4627 : : /*
4628 : : * BufferGetLSNAtomic
4629 : : * Retrieves the LSN of the buffer atomically using a buffer header lock.
4630 : : * This is necessary for some callers who may not have an exclusive lock
4631 : : * on the buffer.
4632 : : */
4633 : : XLogRecPtr
4634 : 950571 : BufferGetLSNAtomic(Buffer buffer)
4635 : : {
4636 : 950571 : char *page = BufferGetPage(buffer);
4637 : 950571 : BufferDesc *bufHdr;
4638 : 950571 : XLogRecPtr lsn;
4639 : :
4640 : : /*
4641 : : * If we don't need locking for correctness, fastpath out.
4642 : : */
4643 [ - + + + ]: 950571 : if (!XLogHintBitIsNeeded() || BufferIsLocal(buffer))
4644 : 26769 : return PageGetLSN(page);
4645 : :
4646 : : /* Make sure we've got a real buffer, and that we hold a pin on it. */
4647 [ + - ]: 923802 : Assert(BufferIsValid(buffer));
4648 [ - + # # : 923802 : Assert(BufferIsPinned(buffer));
- + ]
4649 : :
4650 : 923802 : bufHdr = GetBufferDescriptor(buffer - 1);
4651 : 923802 : LockBufHdr(bufHdr);
4652 : 923802 : lsn = PageGetLSN(page);
4653 : 923802 : UnlockBufHdr(bufHdr);
4654 : :
4655 : 923802 : return lsn;
4656 : 950571 : }
4657 : :
4658 : : /* ---------------------------------------------------------------------
4659 : : * DropRelationBuffers
4660 : : *
4661 : : * This function removes from the buffer pool all the pages of the
4662 : : * specified relation forks that have block numbers >= firstDelBlock.
4663 : : * (In particular, with firstDelBlock = 0, all pages are removed.)
4664 : : * Dirty pages are simply dropped, without bothering to write them
4665 : : * out first. Therefore, this is NOT rollback-able, and so should be
4666 : : * used only with extreme caution!
4667 : : *
4668 : : * Currently, this is called only from smgr.c when the underlying file
4669 : : * is about to be deleted or truncated (firstDelBlock is needed for
4670 : : * the truncation case). The data in the affected pages would therefore
4671 : : * be deleted momentarily anyway, and there is no point in writing it.
4672 : : * It is the responsibility of higher-level code to ensure that the
4673 : : * deletion or truncation does not lose any data that could be needed
4674 : : * later. It is also the responsibility of higher-level code to ensure
4675 : : * that no other process could be trying to load more pages of the
4676 : : * relation into buffers.
4677 : : * --------------------------------------------------------------------
4678 : : */
4679 : : void
4680 : 155 : DropRelationBuffers(SMgrRelation smgr_reln, ForkNumber *forkNum,
4681 : : int nforks, BlockNumber *firstDelBlock)
4682 : : {
4683 : 155 : int i;
4684 : 155 : int j;
4685 : 155 : RelFileLocatorBackend rlocator;
4686 : 155 : BlockNumber nForkBlock[MAX_FORKNUM];
4687 : 155 : uint64 nBlocksToInvalidate = 0;
4688 : :
4689 : 155 : rlocator = smgr_reln->smgr_rlocator;
4690 : :
4691 : : /* If it's a local relation, it's localbuf.c's problem. */
4692 [ + + ]: 155 : if (RelFileLocatorBackendIsTemp(rlocator))
4693 : : {
4694 [ - + ]: 123 : if (rlocator.backend == MyProcNumber)
4695 : 246 : DropRelationLocalBuffers(rlocator.locator, forkNum, nforks,
4696 : 123 : firstDelBlock);
4697 : :
4698 : 123 : return;
4699 : : }
4700 : :
4701 : : /*
4702 : : * To remove all the pages of the specified relation forks from the buffer
4703 : : * pool, we need to scan the entire buffer pool but we can optimize it by
4704 : : * finding the buffers from BufMapping table provided we know the exact
4705 : : * size of each fork of the relation. The exact size is required to ensure
4706 : : * that we don't leave any buffer for the relation being dropped as
4707 : : * otherwise the background writer or checkpointer can lead to a PANIC
4708 : : * error while flushing buffers corresponding to files that don't exist.
4709 : : *
4710 : : * To know the exact size, we rely on the size cached for each fork by us
4711 : : * during recovery which limits the optimization to recovery and on
4712 : : * standbys but we can easily extend it once we have shared cache for
4713 : : * relation size.
4714 : : *
4715 : : * In recovery, we cache the value returned by the first lseek(SEEK_END)
4716 : : * and the future writes keeps the cached value up-to-date. See
4717 : : * smgrextend. It is possible that the value of the first lseek is smaller
4718 : : * than the actual number of existing blocks in the file due to buggy
4719 : : * Linux kernels that might not have accounted for the recent write. But
4720 : : * that should be fine because there must not be any buffers after that
4721 : : * file size.
4722 : : */
4723 [ - + ]: 32 : for (i = 0; i < nforks; i++)
4724 : : {
4725 : : /* Get the number of blocks for a relation's fork */
4726 : 32 : nForkBlock[i] = smgrnblocks_cached(smgr_reln, forkNum[i]);
4727 : :
4728 [ + - ]: 32 : if (nForkBlock[i] == InvalidBlockNumber)
4729 : : {
4730 : 32 : nBlocksToInvalidate = InvalidBlockNumber;
4731 : 32 : break;
4732 : : }
4733 : :
4734 : : /* calculate the number of blocks to be invalidated */
4735 : 0 : nBlocksToInvalidate += (nForkBlock[i] - firstDelBlock[i]);
4736 : 0 : }
4737 : :
4738 : : /*
4739 : : * We apply the optimization iff the total number of blocks to invalidate
4740 : : * is below the BUF_DROP_FULL_SCAN_THRESHOLD.
4741 : : */
4742 [ - + # # ]: 32 : if (BlockNumberIsValid(nBlocksToInvalidate) &&
4743 : 0 : nBlocksToInvalidate < BUF_DROP_FULL_SCAN_THRESHOLD)
4744 : : {
4745 [ # # ]: 0 : for (j = 0; j < nforks; j++)
4746 : 0 : FindAndDropRelationBuffers(rlocator.locator, forkNum[j],
4747 : 0 : nForkBlock[j], firstDelBlock[j]);
4748 : 0 : return;
4749 : : }
4750 : :
4751 [ + + ]: 524320 : for (i = 0; i < NBuffers; i++)
4752 : : {
4753 : 524288 : BufferDesc *bufHdr = GetBufferDescriptor(i);
4754 : :
4755 : : /*
4756 : : * We can make this a tad faster by prechecking the buffer tag before
4757 : : * we attempt to lock the buffer; this saves a lot of lock
4758 : : * acquisitions in typical cases. It should be safe because the
4759 : : * caller must have AccessExclusiveLock on the relation, or some other
4760 : : * reason to be certain that no one is loading new pages of the rel
4761 : : * into the buffer pool. (Otherwise we might well miss such pages
4762 : : * entirely.) Therefore, while the tag might be changing while we
4763 : : * look at it, it can't be changing *to* a value we care about, only
4764 : : * *away* from such a value. So false negatives are impossible, and
4765 : : * false positives are safe because we'll recheck after getting the
4766 : : * buffer lock.
4767 : : *
4768 : : * We could check forkNum and blockNum as well as the rlocator, but
4769 : : * the incremental win from doing so seems small.
4770 : : */
4771 [ + + ]: 524288 : if (!BufTagMatchesRelFileLocator(&bufHdr->tag, &rlocator.locator))
4772 : 522561 : continue;
4773 : :
4774 : 1727 : LockBufHdr(bufHdr);
4775 : :
4776 [ + + ]: 4530 : for (j = 0; j < nforks; j++)
4777 : : {
4778 [ + - ]: 3151 : if (BufTagMatchesRelFileLocator(&bufHdr->tag, &rlocator.locator) &&
4779 [ + + + + ]: 3151 : BufTagGetForkNum(&bufHdr->tag) == forkNum[j] &&
4780 : 1707 : bufHdr->tag.blockNum >= firstDelBlock[j])
4781 : : {
4782 : 348 : InvalidateBuffer(bufHdr); /* releases spinlock */
4783 : 348 : break;
4784 : : }
4785 : 2803 : }
4786 [ + + ]: 1727 : if (j >= nforks)
4787 : 1379 : UnlockBufHdr(bufHdr);
4788 [ + + ]: 524288 : }
4789 : 155 : }
4790 : :
4791 : : /* ---------------------------------------------------------------------
4792 : : * DropRelationsAllBuffers
4793 : : *
4794 : : * This function removes from the buffer pool all the pages of all
4795 : : * forks of the specified relations. It's equivalent to calling
4796 : : * DropRelationBuffers once per fork per relation with firstDelBlock = 0.
4797 : : * --------------------------------------------------------------------
4798 : : */
4799 : : void
4800 : 2704 : DropRelationsAllBuffers(SMgrRelation *smgr_reln, int nlocators)
4801 : : {
4802 : 2704 : int i;
4803 : 2704 : int n = 0;
4804 : 2704 : SMgrRelation *rels;
4805 : 2704 : BlockNumber (*block)[MAX_FORKNUM + 1];
4806 : 2704 : uint64 nBlocksToInvalidate = 0;
4807 : 2704 : RelFileLocator *locators;
4808 : 2704 : bool cached = true;
4809 : 2704 : bool use_bsearch;
4810 : :
4811 [ + - ]: 2704 : if (nlocators == 0)
4812 : 0 : return;
4813 : :
4814 : 2704 : rels = palloc_array(SMgrRelation, nlocators); /* non-local relations */
4815 : :
4816 : : /* If it's a local relation, it's localbuf.c's problem. */
4817 [ + + ]: 11628 : for (i = 0; i < nlocators; i++)
4818 : : {
4819 [ + + ]: 8924 : if (RelFileLocatorBackendIsTemp(smgr_reln[i]->smgr_rlocator))
4820 : : {
4821 [ - + ]: 1012 : if (smgr_reln[i]->smgr_rlocator.backend == MyProcNumber)
4822 : 1012 : DropRelationAllLocalBuffers(smgr_reln[i]->smgr_rlocator.locator);
4823 : 1012 : }
4824 : : else
4825 : 7912 : rels[n++] = smgr_reln[i];
4826 : 8924 : }
4827 : :
4828 : : /*
4829 : : * If there are no non-local relations, then we're done. Release the
4830 : : * memory and return.
4831 : : */
4832 [ + + ]: 2704 : if (n == 0)
4833 : : {
4834 : 257 : pfree(rels);
4835 : 257 : return;
4836 : : }
4837 : :
4838 : : /*
4839 : : * This is used to remember the number of blocks for all the relations
4840 : : * forks.
4841 : : */
4842 : 2447 : block = (BlockNumber (*)[MAX_FORKNUM + 1])
4843 : 2447 : palloc(sizeof(BlockNumber) * n * (MAX_FORKNUM + 1));
4844 : :
4845 : : /*
4846 : : * We can avoid scanning the entire buffer pool if we know the exact size
4847 : : * of each of the given relation forks. See DropRelationBuffers.
4848 : : */
4849 [ + + + + ]: 4895 : for (i = 0; i < n && cached; i++)
4850 : : {
4851 [ + + ]: 4899 : for (int j = 0; j <= MAX_FORKNUM; j++)
4852 : : {
4853 : : /* Get the number of blocks for a relation's fork. */
4854 : 2451 : block[i][j] = smgrnblocks_cached(rels[i], j);
4855 : :
4856 : : /* We need to only consider the relation forks that exists. */
4857 [ - + ]: 2451 : if (block[i][j] == InvalidBlockNumber)
4858 : : {
4859 [ + + ]: 2451 : if (!smgrexists(rels[i], j))
4860 : 4 : continue;
4861 : 2447 : cached = false;
4862 : 2447 : break;
4863 : : }
4864 : :
4865 : : /* calculate the total number of blocks to be invalidated */
4866 : 0 : nBlocksToInvalidate += block[i][j];
4867 : 0 : }
4868 : 2448 : }
4869 : :
4870 : : /*
4871 : : * We apply the optimization iff the total number of blocks to invalidate
4872 : : * is below the BUF_DROP_FULL_SCAN_THRESHOLD.
4873 : : */
4874 [ - + # # ]: 2447 : if (cached && nBlocksToInvalidate < BUF_DROP_FULL_SCAN_THRESHOLD)
4875 : : {
4876 [ # # ]: 0 : for (i = 0; i < n; i++)
4877 : : {
4878 [ # # ]: 0 : for (int j = 0; j <= MAX_FORKNUM; j++)
4879 : : {
4880 : : /* ignore relation forks that doesn't exist */
4881 [ # # ]: 0 : if (!BlockNumberIsValid(block[i][j]))
4882 : 0 : continue;
4883 : :
4884 : : /* drop all the buffers for a particular relation fork */
4885 : 0 : FindAndDropRelationBuffers(rels[i]->smgr_rlocator.locator,
4886 : 0 : j, block[i][j], 0);
4887 : 0 : }
4888 : 0 : }
4889 : :
4890 : 0 : pfree(block);
4891 : 0 : pfree(rels);
4892 : 0 : return;
4893 : : }
4894 : :
4895 : 2447 : pfree(block);
4896 : 2447 : locators = palloc_array(RelFileLocator, n); /* non-local relations */
4897 [ + + ]: 10359 : for (i = 0; i < n; i++)
4898 : 7912 : locators[i] = rels[i]->smgr_rlocator.locator;
4899 : :
4900 : : /*
4901 : : * For low number of relations to drop just use a simple walk through, to
4902 : : * save the bsearch overhead. The threshold to use is rather a guess than
4903 : : * an exactly determined value, as it depends on many factors (CPU and RAM
4904 : : * speeds, amount of shared buffers etc.).
4905 : : */
4906 : 2447 : use_bsearch = n > RELS_BSEARCH_THRESHOLD;
4907 : :
4908 : : /* sort the list of rlocators if necessary */
4909 [ + + ]: 2447 : if (use_bsearch)
4910 : 29 : qsort(locators, n, sizeof(RelFileLocator), rlocator_comparator);
4911 : :
4912 [ + + ]: 40094095 : for (i = 0; i < NBuffers; i++)
4913 : : {
4914 : 40091648 : RelFileLocator *rlocator = NULL;
4915 : 40091648 : BufferDesc *bufHdr = GetBufferDescriptor(i);
4916 : :
4917 : : /*
4918 : : * As in DropRelationBuffers, an unlocked precheck should be safe and
4919 : : * saves some cycles.
4920 : : */
4921 : :
4922 [ + + ]: 40091648 : if (!use_bsearch)
4923 : : {
4924 : 39616512 : int j;
4925 : :
4926 [ + + ]: 152914393 : for (j = 0; j < n; j++)
4927 : : {
4928 [ + + ]: 113315049 : if (BufTagMatchesRelFileLocator(&bufHdr->tag, &locators[j]))
4929 : : {
4930 : 17168 : rlocator = &locators[j];
4931 : 17168 : break;
4932 : : }
4933 : 113297881 : }
4934 : 39616512 : }
4935 : : else
4936 : : {
4937 : 475136 : RelFileLocator locator;
4938 : :
4939 : 475136 : locator = BufTagGetRelFileLocator(&bufHdr->tag);
4940 : 475136 : rlocator = bsearch(&locator,
4941 : 475136 : locators, n, sizeof(RelFileLocator),
4942 : : rlocator_comparator);
4943 : 475136 : }
4944 : :
4945 : : /* buffer doesn't belong to any of the given relfilelocators; skip it */
4946 [ + + ]: 40091648 : if (rlocator == NULL)
4947 : 40073942 : continue;
4948 : :
4949 : 17706 : LockBufHdr(bufHdr);
4950 [ + - ]: 17706 : if (BufTagMatchesRelFileLocator(&bufHdr->tag, rlocator))
4951 : 17706 : InvalidateBuffer(bufHdr); /* releases spinlock */
4952 : : else
4953 : 0 : UnlockBufHdr(bufHdr);
4954 [ + + ]: 40091648 : }
4955 : :
4956 : 2447 : pfree(locators);
4957 : 2447 : pfree(rels);
4958 : 2704 : }
4959 : :
4960 : : /* ---------------------------------------------------------------------
4961 : : * FindAndDropRelationBuffers
4962 : : *
4963 : : * This function performs look up in BufMapping table and removes from the
4964 : : * buffer pool all the pages of the specified relation fork that has block
4965 : : * number >= firstDelBlock. (In particular, with firstDelBlock = 0, all
4966 : : * pages are removed.)
4967 : : * --------------------------------------------------------------------
4968 : : */
4969 : : static void
4970 : 0 : FindAndDropRelationBuffers(RelFileLocator rlocator, ForkNumber forkNum,
4971 : : BlockNumber nForkBlock,
4972 : : BlockNumber firstDelBlock)
4973 : : {
4974 : 0 : BlockNumber curBlock;
4975 : :
4976 [ # # ]: 0 : for (curBlock = firstDelBlock; curBlock < nForkBlock; curBlock++)
4977 : : {
4978 : 0 : uint32 bufHash; /* hash value for tag */
4979 : 0 : BufferTag bufTag; /* identity of requested block */
4980 : 0 : LWLock *bufPartitionLock; /* buffer partition lock for it */
4981 : 0 : int buf_id;
4982 : 0 : BufferDesc *bufHdr;
4983 : :
4984 : : /* create a tag so we can lookup the buffer */
4985 : 0 : InitBufferTag(&bufTag, &rlocator, forkNum, curBlock);
4986 : :
4987 : : /* determine its hash code and partition lock ID */
4988 : 0 : bufHash = BufTableHashCode(&bufTag);
4989 : 0 : bufPartitionLock = BufMappingPartitionLock(bufHash);
4990 : :
4991 : : /* Check that it is in the buffer pool. If not, do nothing. */
4992 : 0 : LWLockAcquire(bufPartitionLock, LW_SHARED);
4993 : 0 : buf_id = BufTableLookup(&bufTag, bufHash);
4994 : 0 : LWLockRelease(bufPartitionLock);
4995 : :
4996 [ # # ]: 0 : if (buf_id < 0)
4997 : 0 : continue;
4998 : :
4999 : 0 : bufHdr = GetBufferDescriptor(buf_id);
5000 : :
5001 : : /*
5002 : : * We need to lock the buffer header and recheck if the buffer is
5003 : : * still associated with the same block because the buffer could be
5004 : : * evicted by some other backend loading blocks for a different
5005 : : * relation after we release lock on the BufMapping table.
5006 : : */
5007 : 0 : LockBufHdr(bufHdr);
5008 : :
5009 [ # # ]: 0 : if (BufTagMatchesRelFileLocator(&bufHdr->tag, &rlocator) &&
5010 [ # # # # ]: 0 : BufTagGetForkNum(&bufHdr->tag) == forkNum &&
5011 : 0 : bufHdr->tag.blockNum >= firstDelBlock)
5012 : 0 : InvalidateBuffer(bufHdr); /* releases spinlock */
5013 : : else
5014 : 0 : UnlockBufHdr(bufHdr);
5015 [ # # # ]: 0 : }
5016 : 0 : }
5017 : :
5018 : : /* ---------------------------------------------------------------------
5019 : : * DropDatabaseBuffers
5020 : : *
5021 : : * This function removes all the buffers in the buffer cache for a
5022 : : * particular database. Dirty pages are simply dropped, without
5023 : : * bothering to write them out first. This is used when we destroy a
5024 : : * database, to avoid trying to flush data to disk when the directory
5025 : : * tree no longer exists. Implementation is pretty similar to
5026 : : * DropRelationBuffers() which is for destroying just one relation.
5027 : : * --------------------------------------------------------------------
5028 : : */
5029 : : void
5030 : 3 : DropDatabaseBuffers(Oid dbid)
5031 : : {
5032 : 3 : int i;
5033 : :
5034 : : /*
5035 : : * We needn't consider local buffers, since by assumption the target
5036 : : * database isn't our own.
5037 : : */
5038 : :
5039 [ + + ]: 49155 : for (i = 0; i < NBuffers; i++)
5040 : : {
5041 : 49152 : BufferDesc *bufHdr = GetBufferDescriptor(i);
5042 : :
5043 : : /*
5044 : : * As in DropRelationBuffers, an unlocked precheck should be safe and
5045 : : * saves some cycles.
5046 : : */
5047 [ + + ]: 49152 : if (bufHdr->tag.dbOid != dbid)
5048 : 48198 : continue;
5049 : :
5050 : 954 : LockBufHdr(bufHdr);
5051 [ + - ]: 954 : if (bufHdr->tag.dbOid == dbid)
5052 : 954 : InvalidateBuffer(bufHdr); /* releases spinlock */
5053 : : else
5054 : 0 : UnlockBufHdr(bufHdr);
5055 [ - + + ]: 49152 : }
5056 : 3 : }
5057 : :
5058 : : /* ---------------------------------------------------------------------
5059 : : * FlushRelationBuffers
5060 : : *
5061 : : * This function writes all dirty pages of a relation out to disk
5062 : : * (or more accurately, out to kernel disk buffers), ensuring that the
5063 : : * kernel has an up-to-date view of the relation.
5064 : : *
5065 : : * Generally, the caller should be holding AccessExclusiveLock on the
5066 : : * target relation to ensure that no other backend is busy dirtying
5067 : : * more blocks of the relation; the effects can't be expected to last
5068 : : * after the lock is released.
5069 : : *
5070 : : * XXX currently it sequentially searches the buffer pool, should be
5071 : : * changed to more clever ways of searching. This routine is not
5072 : : * used in any performance-critical code paths, so it's not worth
5073 : : * adding additional overhead to normal paths to make it go faster.
5074 : : * --------------------------------------------------------------------
5075 : : */
5076 : : void
5077 : 39 : FlushRelationBuffers(Relation rel)
5078 : : {
5079 : 39 : int i;
5080 : 39 : BufferDesc *bufHdr;
5081 : 39 : SMgrRelation srel = RelationGetSmgr(rel);
5082 : :
5083 [ + + ]: 39 : if (RelationUsesLocalBuffers(rel))
5084 : : {
5085 [ + + ]: 303 : for (i = 0; i < NLocBuffer; i++)
5086 : : {
5087 : 300 : uint64 buf_state;
5088 : :
5089 : 300 : bufHdr = GetLocalBufferDescriptor(i);
5090 [ + + - + ]: 300 : if (BufTagMatchesRelFileLocator(&bufHdr->tag, &rel->rd_locator) &&
5091 : 100 : ((buf_state = pg_atomic_read_u64(&bufHdr->state)) &
5092 : 100 : (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
5093 : : {
5094 : 100 : ErrorContextCallback errcallback;
5095 : :
5096 : : /* Setup error traceback support for ereport() */
5097 : 100 : errcallback.callback = local_buffer_write_error_callback;
5098 : 100 : errcallback.arg = bufHdr;
5099 : 100 : errcallback.previous = error_context_stack;
5100 : 100 : error_context_stack = &errcallback;
5101 : :
5102 : : /* Make sure we can handle the pin */
5103 : 100 : ReservePrivateRefCountEntry();
5104 : 100 : ResourceOwnerEnlarge(CurrentResourceOwner);
5105 : :
5106 : : /*
5107 : : * Pin/unpin mostly to make valgrind work, but it also seems
5108 : : * like the right thing to do.
5109 : : */
5110 : 100 : PinLocalBuffer(bufHdr, false);
5111 : :
5112 : :
5113 : 100 : FlushLocalBuffer(bufHdr, srel);
5114 : :
5115 : 100 : UnpinLocalBuffer(BufferDescriptorGetBuffer(bufHdr));
5116 : :
5117 : : /* Pop the error context stack */
5118 : 100 : error_context_stack = errcallback.previous;
5119 : 100 : }
5120 : 300 : }
5121 : :
5122 : 3 : return;
5123 : : }
5124 : :
5125 [ + + ]: 589860 : for (i = 0; i < NBuffers; i++)
5126 : : {
5127 : 589824 : uint64 buf_state;
5128 : :
5129 : 589824 : bufHdr = GetBufferDescriptor(i);
5130 : :
5131 : : /*
5132 : : * As in DropRelationBuffers, an unlocked precheck should be safe and
5133 : : * saves some cycles.
5134 : : */
5135 [ + + ]: 589824 : if (!BufTagMatchesRelFileLocator(&bufHdr->tag, &rel->rd_locator))
5136 : 589769 : continue;
5137 : :
5138 : : /* Make sure we can handle the pin */
5139 : 55 : ReservePrivateRefCountEntry();
5140 : 55 : ResourceOwnerEnlarge(CurrentResourceOwner);
5141 : :
5142 : 55 : buf_state = LockBufHdr(bufHdr);
5143 [ + - + + ]: 55 : if (BufTagMatchesRelFileLocator(&bufHdr->tag, &rel->rd_locator) &&
5144 : 55 : (buf_state & (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
5145 : : {
5146 : 42 : PinBuffer_Locked(bufHdr);
5147 : 42 : FlushUnlockedBuffer(bufHdr, srel, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
5148 : 42 : UnpinBuffer(bufHdr);
5149 : 42 : }
5150 : : else
5151 : 13 : UnlockBufHdr(bufHdr);
5152 [ + + ]: 589824 : }
5153 : 39 : }
5154 : :
5155 : : /* ---------------------------------------------------------------------
5156 : : * FlushRelationsAllBuffers
5157 : : *
5158 : : * This function flushes out of the buffer pool all the pages of all
5159 : : * forks of the specified smgr relations. It's equivalent to calling
5160 : : * FlushRelationBuffers once per relation. The relations are assumed not
5161 : : * to use local buffers.
5162 : : * --------------------------------------------------------------------
5163 : : */
5164 : : void
5165 : 8 : FlushRelationsAllBuffers(SMgrRelation *smgrs, int nrels)
5166 : : {
5167 : 8 : int i;
5168 : 8 : SMgrSortArray *srels;
5169 : 8 : bool use_bsearch;
5170 : :
5171 [ + - ]: 8 : if (nrels == 0)
5172 : 0 : return;
5173 : :
5174 : : /* fill-in array for qsort */
5175 : 8 : srels = palloc_array(SMgrSortArray, nrels);
5176 : :
5177 [ + + ]: 16 : for (i = 0; i < nrels; i++)
5178 : : {
5179 [ + - ]: 8 : Assert(!RelFileLocatorBackendIsTemp(smgrs[i]->smgr_rlocator));
5180 : :
5181 : 8 : srels[i].rlocator = smgrs[i]->smgr_rlocator.locator;
5182 : 8 : srels[i].srel = smgrs[i];
5183 : 8 : }
5184 : :
5185 : : /*
5186 : : * Save the bsearch overhead for low number of relations to sync. See
5187 : : * DropRelationsAllBuffers for details.
5188 : : */
5189 : 8 : use_bsearch = nrels > RELS_BSEARCH_THRESHOLD;
5190 : :
5191 : : /* sort the list of SMgrRelations if necessary */
5192 [ + - ]: 8 : if (use_bsearch)
5193 : 0 : qsort(srels, nrels, sizeof(SMgrSortArray), rlocator_comparator);
5194 : :
5195 [ + + ]: 131080 : for (i = 0; i < NBuffers; i++)
5196 : : {
5197 : 131072 : SMgrSortArray *srelent = NULL;
5198 : 131072 : BufferDesc *bufHdr = GetBufferDescriptor(i);
5199 : 131072 : uint64 buf_state;
5200 : :
5201 : : /*
5202 : : * As in DropRelationBuffers, an unlocked precheck should be safe and
5203 : : * saves some cycles.
5204 : : */
5205 : :
5206 [ - + ]: 131072 : if (!use_bsearch)
5207 : : {
5208 : 131072 : int j;
5209 : :
5210 [ + + ]: 259995 : for (j = 0; j < nrels; j++)
5211 : : {
5212 [ + + ]: 131072 : if (BufTagMatchesRelFileLocator(&bufHdr->tag, &srels[j].rlocator))
5213 : : {
5214 : 2149 : srelent = &srels[j];
5215 : 2149 : break;
5216 : : }
5217 : 128923 : }
5218 : 131072 : }
5219 : : else
5220 : : {
5221 : 0 : RelFileLocator rlocator;
5222 : :
5223 : 0 : rlocator = BufTagGetRelFileLocator(&bufHdr->tag);
5224 : 0 : srelent = bsearch(&rlocator,
5225 : 0 : srels, nrels, sizeof(SMgrSortArray),
5226 : : rlocator_comparator);
5227 : 0 : }
5228 : :
5229 : : /* buffer doesn't belong to any of the given relfilelocators; skip it */
5230 [ + + ]: 131072 : if (srelent == NULL)
5231 : 128923 : continue;
5232 : :
5233 : : /* Make sure we can handle the pin */
5234 : 2149 : ReservePrivateRefCountEntry();
5235 : 2149 : ResourceOwnerEnlarge(CurrentResourceOwner);
5236 : :
5237 : 2149 : buf_state = LockBufHdr(bufHdr);
5238 [ + - + + ]: 2149 : if (BufTagMatchesRelFileLocator(&bufHdr->tag, &srelent->rlocator) &&
5239 : 2149 : (buf_state & (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
5240 : : {
5241 : 1726 : PinBuffer_Locked(bufHdr);
5242 : 1726 : FlushUnlockedBuffer(bufHdr, srelent->srel, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
5243 : 1726 : UnpinBuffer(bufHdr);
5244 : 1726 : }
5245 : : else
5246 : 423 : UnlockBufHdr(bufHdr);
5247 [ + + ]: 131072 : }
5248 : :
5249 : 8 : pfree(srels);
5250 : 8 : }
5251 : :
5252 : : /* ---------------------------------------------------------------------
5253 : : * RelationCopyStorageUsingBuffer
5254 : : *
5255 : : * Copy fork's data using bufmgr. Same as RelationCopyStorage but instead
5256 : : * of using smgrread and smgrextend this will copy using bufmgr APIs.
5257 : : *
5258 : : * Refer comments atop CreateAndCopyRelationData() for details about
5259 : : * 'permanent' parameter.
5260 : : * --------------------------------------------------------------------
5261 : : */
5262 : : static void
5263 : 894 : RelationCopyStorageUsingBuffer(RelFileLocator srclocator,
5264 : : RelFileLocator dstlocator,
5265 : : ForkNumber forkNum, bool permanent)
5266 : : {
5267 : 894 : Buffer srcBuf;
5268 : 894 : Buffer dstBuf;
5269 : 894 : Page srcPage;
5270 : 894 : Page dstPage;
5271 : 894 : bool use_wal;
5272 : 894 : BlockNumber nblocks;
5273 : 894 : BlockNumber blkno;
5274 : 894 : PGIOAlignedBlock buf;
5275 : 894 : BufferAccessStrategy bstrategy_src;
5276 : 894 : BufferAccessStrategy bstrategy_dst;
5277 : 894 : BlockRangeReadStreamPrivate p;
5278 : 894 : ReadStream *src_stream;
5279 : 894 : SMgrRelation src_smgr;
5280 : :
5281 : : /*
5282 : : * In general, we want to write WAL whenever wal_level > 'minimal', but we
5283 : : * can skip it when copying any fork of an unlogged relation other than
5284 : : * the init fork.
5285 : : */
5286 [ + + + - ]: 1192 : use_wal = XLogIsNeeded() && (permanent || forkNum == INIT_FORKNUM);
5287 : :
5288 : : /* Get number of blocks in the source relation. */
5289 : 1788 : nblocks = smgrnblocks(smgropen(srclocator, INVALID_PROC_NUMBER),
5290 : 894 : forkNum);
5291 : :
5292 : : /* Nothing to copy; just return. */
5293 [ + + ]: 894 : if (nblocks == 0)
5294 : 156 : return;
5295 : :
5296 : : /*
5297 : : * Bulk extend the destination relation of the same size as the source
5298 : : * relation before starting to copy block by block.
5299 : : */
5300 : 738 : memset(buf.data, 0, BLCKSZ);
5301 : 1476 : smgrextend(smgropen(dstlocator, INVALID_PROC_NUMBER), forkNum, nblocks - 1,
5302 : 738 : buf.data, true);
5303 : :
5304 : : /* This is a bulk operation, so use buffer access strategies. */
5305 : 738 : bstrategy_src = GetAccessStrategy(BAS_BULKREAD);
5306 : 738 : bstrategy_dst = GetAccessStrategy(BAS_BULKWRITE);
5307 : :
5308 : : /* Initialize streaming read */
5309 : 738 : p.current_blocknum = 0;
5310 : 738 : p.last_exclusive = nblocks;
5311 : 738 : src_smgr = smgropen(srclocator, INVALID_PROC_NUMBER);
5312 : :
5313 : : /*
5314 : : * It is safe to use batchmode as block_range_read_stream_cb takes no
5315 : : * locks.
5316 : : */
5317 : 738 : src_stream = read_stream_begin_smgr_relation(READ_STREAM_FULL |
5318 : : READ_STREAM_USE_BATCHING,
5319 : 738 : bstrategy_src,
5320 : 738 : src_smgr,
5321 : 738 : permanent ? RELPERSISTENCE_PERMANENT : RELPERSISTENCE_UNLOGGED,
5322 : 738 : forkNum,
5323 : : block_range_read_stream_cb,
5324 : : &p,
5325 : : 0);
5326 : :
5327 : : /* Iterate over each block of the source relation file. */
5328 [ + + ]: 3600 : for (blkno = 0; blkno < nblocks; blkno++)
5329 : : {
5330 [ + - ]: 2862 : CHECK_FOR_INTERRUPTS();
5331 : :
5332 : : /* Read block from source relation. */
5333 : 2862 : srcBuf = read_stream_next_buffer(src_stream, NULL);
5334 : 2862 : LockBuffer(srcBuf, BUFFER_LOCK_SHARE);
5335 : 2862 : srcPage = BufferGetPage(srcBuf);
5336 : :
5337 : 5724 : dstBuf = ReadBufferWithoutRelcache(dstlocator, forkNum,
5338 : 2862 : BufferGetBlockNumber(srcBuf),
5339 : 2862 : RBM_ZERO_AND_LOCK, bstrategy_dst,
5340 : 2862 : permanent);
5341 : 2862 : dstPage = BufferGetPage(dstBuf);
5342 : :
5343 : 2862 : START_CRIT_SECTION();
5344 : :
5345 : : /* Copy page data from the source to the destination. */
5346 : 2862 : memcpy(dstPage, srcPage, BLCKSZ);
5347 : 2862 : MarkBufferDirty(dstBuf);
5348 : :
5349 : : /* WAL-log the copied page. */
5350 [ + + ]: 2862 : if (use_wal)
5351 : 954 : log_newpage_buffer(dstBuf, true);
5352 : :
5353 [ + - ]: 2862 : END_CRIT_SECTION();
5354 : :
5355 : 2862 : UnlockReleaseBuffer(dstBuf);
5356 : 2862 : UnlockReleaseBuffer(srcBuf);
5357 : 2862 : }
5358 [ + - ]: 738 : Assert(read_stream_next_buffer(src_stream, NULL) == InvalidBuffer);
5359 : 738 : read_stream_end(src_stream);
5360 : :
5361 : 738 : FreeAccessStrategy(bstrategy_src);
5362 : 738 : FreeAccessStrategy(bstrategy_dst);
5363 [ - + ]: 894 : }
5364 : :
5365 : : /* ---------------------------------------------------------------------
5366 : : * CreateAndCopyRelationData
5367 : : *
5368 : : * Create destination relation storage and copy all forks from the
5369 : : * source relation to the destination.
5370 : : *
5371 : : * Pass permanent as true for permanent relations and false for
5372 : : * unlogged relations. Currently this API is not supported for
5373 : : * temporary relations.
5374 : : * --------------------------------------------------------------------
5375 : : */
5376 : : void
5377 : 672 : CreateAndCopyRelationData(RelFileLocator src_rlocator,
5378 : : RelFileLocator dst_rlocator, bool permanent)
5379 : : {
5380 : 672 : char relpersistence;
5381 : 672 : SMgrRelation src_rel;
5382 : 672 : SMgrRelation dst_rel;
5383 : :
5384 : : /* Set the relpersistence. */
5385 : 672 : relpersistence = permanent ?
5386 : : RELPERSISTENCE_PERMANENT : RELPERSISTENCE_UNLOGGED;
5387 : :
5388 : 672 : src_rel = smgropen(src_rlocator, INVALID_PROC_NUMBER);
5389 : 672 : dst_rel = smgropen(dst_rlocator, INVALID_PROC_NUMBER);
5390 : :
5391 : : /*
5392 : : * Create and copy all forks of the relation. During create database we
5393 : : * have a separate cleanup mechanism which deletes complete database
5394 : : * directory. Therefore, each individual relation doesn't need to be
5395 : : * registered for cleanup.
5396 : : */
5397 : 672 : RelationCreateStorage(dst_rlocator, relpersistence, false);
5398 : :
5399 : : /* copy main fork. */
5400 : 672 : RelationCopyStorageUsingBuffer(src_rlocator, dst_rlocator, MAIN_FORKNUM,
5401 : 672 : permanent);
5402 : :
5403 : : /* copy those extra forks that exist */
5404 [ + + ]: 2688 : for (ForkNumber forkNum = MAIN_FORKNUM + 1;
5405 : 2688 : forkNum <= MAX_FORKNUM; forkNum++)
5406 : : {
5407 [ + + ]: 2016 : if (smgrexists(src_rel, forkNum))
5408 : : {
5409 : 222 : smgrcreate(dst_rel, forkNum, false);
5410 : :
5411 : : /*
5412 : : * WAL log creation if the relation is persistent, or this is the
5413 : : * init fork of an unlogged relation.
5414 : : */
5415 [ - + # # ]: 222 : if (permanent || forkNum == INIT_FORKNUM)
5416 : 222 : log_smgrcreate(&dst_rlocator, forkNum);
5417 : :
5418 : : /* Copy a fork's data, block by block. */
5419 : 444 : RelationCopyStorageUsingBuffer(src_rlocator, dst_rlocator, forkNum,
5420 : 222 : permanent);
5421 : 222 : }
5422 : 2016 : }
5423 : 672 : }
5424 : :
5425 : : /* ---------------------------------------------------------------------
5426 : : * FlushDatabaseBuffers
5427 : : *
5428 : : * This function writes all dirty pages of a database out to disk
5429 : : * (or more accurately, out to kernel disk buffers), ensuring that the
5430 : : * kernel has an up-to-date view of the database.
5431 : : *
5432 : : * Generally, the caller should be holding an appropriate lock to ensure
5433 : : * no other backend is active in the target database; otherwise more
5434 : : * pages could get dirtied.
5435 : : *
5436 : : * Note we don't worry about flushing any pages of temporary relations.
5437 : : * It's assumed these wouldn't be interesting.
5438 : : * --------------------------------------------------------------------
5439 : : */
5440 : : void
5441 : 0 : FlushDatabaseBuffers(Oid dbid)
5442 : : {
5443 : 0 : int i;
5444 : 0 : BufferDesc *bufHdr;
5445 : :
5446 [ # # ]: 0 : for (i = 0; i < NBuffers; i++)
5447 : : {
5448 : 0 : uint64 buf_state;
5449 : :
5450 : 0 : bufHdr = GetBufferDescriptor(i);
5451 : :
5452 : : /*
5453 : : * As in DropRelationBuffers, an unlocked precheck should be safe and
5454 : : * saves some cycles.
5455 : : */
5456 [ # # ]: 0 : if (bufHdr->tag.dbOid != dbid)
5457 : 0 : continue;
5458 : :
5459 : : /* Make sure we can handle the pin */
5460 : 0 : ReservePrivateRefCountEntry();
5461 : 0 : ResourceOwnerEnlarge(CurrentResourceOwner);
5462 : :
5463 : 0 : buf_state = LockBufHdr(bufHdr);
5464 [ # # # # ]: 0 : if (bufHdr->tag.dbOid == dbid &&
5465 : 0 : (buf_state & (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
5466 : : {
5467 : 0 : PinBuffer_Locked(bufHdr);
5468 : 0 : FlushUnlockedBuffer(bufHdr, NULL, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
5469 : 0 : UnpinBuffer(bufHdr);
5470 : 0 : }
5471 : : else
5472 : 0 : UnlockBufHdr(bufHdr);
5473 [ # # # ]: 0 : }
5474 : 0 : }
5475 : :
5476 : : /*
5477 : : * Flush a previously, shared or exclusively, locked and pinned buffer to the
5478 : : * OS.
5479 : : */
5480 : : void
5481 : 0 : FlushOneBuffer(Buffer buffer)
5482 : : {
5483 : 0 : BufferDesc *bufHdr;
5484 : :
5485 : : /* currently not needed, but no fundamental reason not to support */
5486 [ # # ]: 0 : Assert(!BufferIsLocal(buffer));
5487 : :
5488 [ # # # # : 0 : Assert(BufferIsPinned(buffer));
# # ]
5489 : :
5490 : 0 : bufHdr = GetBufferDescriptor(buffer - 1);
5491 : :
5492 [ # # ]: 0 : Assert(BufferIsLockedByMe(buffer));
5493 : :
5494 : 0 : FlushBuffer(bufHdr, NULL, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
5495 : 0 : }
5496 : :
5497 : : /*
5498 : : * ReleaseBuffer -- release the pin on a buffer
5499 : : */
5500 : : void
5501 : 12195514 : ReleaseBuffer(Buffer buffer)
5502 : : {
5503 [ + - ]: 12195514 : if (!BufferIsValid(buffer))
5504 [ # # # # ]: 0 : elog(ERROR, "bad buffer ID: %d", buffer);
5505 : :
5506 [ + + ]: 12195514 : if (BufferIsLocal(buffer))
5507 : 460412 : UnpinLocalBuffer(buffer);
5508 : : else
5509 : 11735102 : UnpinBuffer(GetBufferDescriptor(buffer - 1));
5510 : 12195514 : }
5511 : :
5512 : : /*
5513 : : * UnlockReleaseBuffer -- release the content lock and pin on a buffer
5514 : : *
5515 : : * This is just a shorthand for a common combination.
5516 : : */
5517 : : void
5518 : 2621155 : UnlockReleaseBuffer(Buffer buffer)
5519 : : {
5520 : 2621155 : LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
5521 : 2621155 : ReleaseBuffer(buffer);
5522 : 2621155 : }
5523 : :
5524 : : /*
5525 : : * IncrBufferRefCount
5526 : : * Increment the pin count on a buffer that we have *already* pinned
5527 : : * at least once.
5528 : : *
5529 : : * This function cannot be used on a buffer we do not have pinned,
5530 : : * because it doesn't change the shared buffer state.
5531 : : */
5532 : : void
5533 : 2413916 : IncrBufferRefCount(Buffer buffer)
5534 : : {
5535 [ - + # # : 2413916 : Assert(BufferIsPinned(buffer));
+ + ]
5536 : 2413916 : ResourceOwnerEnlarge(CurrentResourceOwner);
5537 [ + + ]: 2413916 : if (BufferIsLocal(buffer))
5538 : 114637 : LocalRefCount[-buffer - 1]++;
5539 : : else
5540 : : {
5541 : 2299279 : PrivateRefCountEntry *ref;
5542 : :
5543 : 2299279 : ref = GetPrivateRefCountEntry(buffer, true);
5544 [ + - ]: 2299279 : Assert(ref != NULL);
5545 : 2299279 : ref->data.refcount++;
5546 : 2299279 : }
5547 : 2413916 : ResourceOwnerRememberBuffer(CurrentResourceOwner, buffer);
5548 : 2413916 : }
5549 : :
5550 : : /*
5551 : : * MarkBufferDirtyHint
5552 : : *
5553 : : * Mark a buffer dirty for non-critical changes.
5554 : : *
5555 : : * This is essentially the same as MarkBufferDirty, except:
5556 : : *
5557 : : * 1. The caller does not write WAL; so if checksums are enabled, we may need
5558 : : * to write an XLOG_FPI_FOR_HINT WAL record to protect against torn pages.
5559 : : * 2. The caller might have only share-lock instead of exclusive-lock on the
5560 : : * buffer's content lock.
5561 : : * 3. This function does not guarantee that the buffer is always marked dirty
5562 : : * (due to a race condition), so it cannot be used for important changes.
5563 : : */
5564 : : void
5565 : 2059388 : MarkBufferDirtyHint(Buffer buffer, bool buffer_std)
5566 : : {
5567 : 2059388 : BufferDesc *bufHdr;
5568 : 2059388 : Page page = BufferGetPage(buffer);
5569 : :
5570 [ + - ]: 2059388 : if (!BufferIsValid(buffer))
5571 [ # # # # ]: 0 : elog(ERROR, "bad buffer ID: %d", buffer);
5572 : :
5573 [ + + ]: 2059388 : if (BufferIsLocal(buffer))
5574 : : {
5575 : 197225 : MarkLocalBufferDirty(buffer);
5576 : 197225 : return;
5577 : : }
5578 : :
5579 : 1862163 : bufHdr = GetBufferDescriptor(buffer - 1);
5580 : :
5581 [ + - ]: 1862163 : Assert(GetPrivateRefCount(buffer) > 0);
5582 : : /* here, either share or exclusive lock is OK */
5583 [ + - ]: 1862163 : Assert(BufferIsLockedByMe(buffer));
5584 : :
5585 : : /*
5586 : : * This routine might get called many times on the same page, if we are
5587 : : * making the first scan after commit of an xact that added/deleted many
5588 : : * tuples. So, be as quick as we can if the buffer is already dirty. We
5589 : : * do this by not acquiring spinlock if it looks like the status bits are
5590 : : * already set. Since we make this test unlocked, there's a chance we
5591 : : * might fail to notice that the flags have just been cleared, and failed
5592 : : * to reset them, due to memory-ordering issues. But since this function
5593 : : * is only intended to be used in cases where failing to write out the
5594 : : * data would be harmless anyway, it doesn't really matter.
5595 : : */
5596 [ + + ]: 1862163 : if ((pg_atomic_read_u64(&bufHdr->state) & (BM_DIRTY | BM_JUST_DIRTIED)) !=
5597 : : (BM_DIRTY | BM_JUST_DIRTIED))
5598 : : {
5599 : 4953 : XLogRecPtr lsn = InvalidXLogRecPtr;
5600 : 4953 : bool dirtied = false;
5601 : 4953 : bool delayChkptFlags = false;
5602 : 4953 : uint64 buf_state;
5603 : :
5604 : : /*
5605 : : * If we need to protect hint bit updates from torn writes, WAL-log a
5606 : : * full page image of the page. This full page image is only necessary
5607 : : * if the hint bit update is the first change to the page since the
5608 : : * last checkpoint.
5609 : : *
5610 : : * We don't check full_page_writes here because that logic is included
5611 : : * when we call XLogInsert() since the value changes dynamically.
5612 : : */
5613 [ - + + + ]: 4953 : if (XLogHintBitIsNeeded() &&
5614 : 4953 : (pg_atomic_read_u64(&bufHdr->state) & BM_PERMANENT))
5615 : : {
5616 : : /*
5617 : : * If we must not write WAL, due to a relfilelocator-specific
5618 : : * condition or being in recovery, don't dirty the page. We can
5619 : : * set the hint, just not dirty the page as a result so the hint
5620 : : * is lost when we evict the page or shutdown.
5621 : : *
5622 : : * See src/backend/storage/page/README for longer discussion.
5623 : : */
5624 [ + - + + ]: 4950 : if (RecoveryInProgress() ||
5625 : 4950 : RelFileLocatorSkippingWAL(BufTagGetRelFileLocator(&bufHdr->tag)))
5626 : 1637 : return;
5627 : :
5628 : : /*
5629 : : * If the block is already dirty because we either made a change
5630 : : * or set a hint already, then we don't need to write a full page
5631 : : * image. Note that aggressive cleaning of blocks dirtied by hint
5632 : : * bit setting would increase the call rate. Bulk setting of hint
5633 : : * bits would reduce the call rate...
5634 : : *
5635 : : * We must issue the WAL record before we mark the buffer dirty.
5636 : : * Otherwise we might write the page before we write the WAL. That
5637 : : * causes a race condition, since a checkpoint might occur between
5638 : : * writing the WAL record and marking the buffer dirty. We solve
5639 : : * that with a kluge, but one that is already in use during
5640 : : * transaction commit to prevent race conditions. Basically, we
5641 : : * simply prevent the checkpoint WAL record from being written
5642 : : * until we have marked the buffer dirty. We don't start the
5643 : : * checkpoint flush until we have marked dirty, so our checkpoint
5644 : : * must flush the change to disk successfully or the checkpoint
5645 : : * never gets written, so crash recovery will fix.
5646 : : *
5647 : : * It's possible we may enter here without an xid, so it is
5648 : : * essential that CreateCheckPoint waits for virtual transactions
5649 : : * rather than full transactionids.
5650 : : */
5651 [ + - ]: 3313 : Assert((MyProc->delayChkptFlags & DELAY_CHKPT_START) == 0);
5652 : 3313 : MyProc->delayChkptFlags |= DELAY_CHKPT_START;
5653 : 3313 : delayChkptFlags = true;
5654 : 3313 : lsn = XLogSaveBufferForHint(buffer, buffer_std);
5655 : 3313 : }
5656 : :
5657 : 3316 : buf_state = LockBufHdr(bufHdr);
5658 : :
5659 [ + - ]: 3316 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
5660 : :
5661 [ - + ]: 3316 : if (!(buf_state & BM_DIRTY))
5662 : : {
5663 : 3316 : dirtied = true; /* Means "will be dirtied by this action" */
5664 : :
5665 : : /*
5666 : : * Set the page LSN if we wrote a backup block. We aren't supposed
5667 : : * to set this when only holding a share lock but as long as we
5668 : : * serialise it somehow we're OK. We choose to set LSN while
5669 : : * holding the buffer header lock, which causes any reader of an
5670 : : * LSN who holds only a share lock to also obtain a buffer header
5671 : : * lock before using PageGetLSN(), which is enforced in
5672 : : * BufferGetLSNAtomic().
5673 : : *
5674 : : * If checksums are enabled, you might think we should reset the
5675 : : * checksum here. That will happen when the page is written
5676 : : * sometime later in this checkpoint cycle.
5677 : : */
5678 [ + + ]: 3316 : if (XLogRecPtrIsValid(lsn))
5679 : 3282 : PageSetLSN(page, lsn);
5680 : 3316 : }
5681 : :
5682 : 3316 : UnlockBufHdrExt(bufHdr, buf_state,
5683 : : BM_DIRTY | BM_JUST_DIRTIED,
5684 : : 0, 0);
5685 : :
5686 [ + + ]: 3316 : if (delayChkptFlags)
5687 : 3313 : MyProc->delayChkptFlags &= ~DELAY_CHKPT_START;
5688 : :
5689 [ - + ]: 3316 : if (dirtied)
5690 : : {
5691 : 3316 : pgBufferUsage.shared_blks_dirtied++;
5692 [ + - ]: 3316 : if (VacuumCostActive)
5693 : 0 : VacuumCostBalance += VacuumCostPageDirty;
5694 : 3316 : }
5695 [ + + ]: 4953 : }
5696 [ - + ]: 2059388 : }
5697 : :
5698 : : /*
5699 : : * Release buffer content locks for shared buffers.
5700 : : *
5701 : : * Used to clean up after errors.
5702 : : *
5703 : : * Currently, we can expect that resource owner cleanup, via
5704 : : * ResOwnerReleaseBufferPin(), took care of releasing buffer content locks per
5705 : : * se; the only thing we need to deal with here is clearing any PIN_COUNT
5706 : : * request that was in progress.
5707 : : */
5708 : : void
5709 : 9005 : UnlockBuffers(void)
5710 : : {
5711 : 9005 : BufferDesc *buf = PinCountWaitBuf;
5712 : :
5713 [ + - ]: 9005 : if (buf)
5714 : : {
5715 : 0 : uint64 buf_state;
5716 : 0 : uint64 unset_bits = 0;
5717 : :
5718 : 0 : buf_state = LockBufHdr(buf);
5719 : :
5720 : : /*
5721 : : * Don't complain if flag bit not set; it could have been reset but we
5722 : : * got a cancel/die interrupt before getting the signal.
5723 : : */
5724 [ # # # # ]: 0 : if ((buf_state & BM_PIN_COUNT_WAITER) != 0 &&
5725 : 0 : buf->wait_backend_pgprocno == MyProcNumber)
5726 : 0 : unset_bits = BM_PIN_COUNT_WAITER;
5727 : :
5728 : 0 : UnlockBufHdrExt(buf, buf_state,
5729 : 0 : 0, unset_bits,
5730 : : 0);
5731 : :
5732 : 0 : PinCountWaitBuf = NULL;
5733 : 0 : }
5734 : 9005 : }
5735 : :
5736 : : /*
5737 : : * Acquire the buffer content lock in the specified mode
5738 : : *
5739 : : * If the lock is not available, sleep until it is.
5740 : : *
5741 : : * Side effect: cancel/die interrupts are held off until lock release.
5742 : : *
5743 : : * This uses almost the same locking approach as lwlock.c's
5744 : : * LWLockAcquire(). See documentation at the top of lwlock.c for a more
5745 : : * detailed discussion.
5746 : : *
5747 : : * The reason that this, and most of the other BufferLock* functions, get both
5748 : : * the Buffer and BufferDesc* as parameters, is that looking up one from the
5749 : : * other repeatedly shows up noticeably in profiles.
5750 : : *
5751 : : * Callers should provide a constant for mode, for more efficient code
5752 : : * generation.
5753 : : */
5754 : : static inline void
5755 : 15028952 : BufferLockAcquire(Buffer buffer, BufferDesc *buf_hdr, BufferLockMode mode)
5756 : : {
5757 : 15028952 : PrivateRefCountEntry *entry;
5758 : 15028952 : int extraWaits = 0;
5759 : :
5760 : : /*
5761 : : * Get reference to the refcount entry before we hold the lock, it seems
5762 : : * better to do before holding the lock.
5763 : : */
5764 : 15028952 : entry = GetPrivateRefCountEntry(buffer, true);
5765 : :
5766 : : /*
5767 : : * We better not already hold a lock on the buffer.
5768 : : */
5769 [ + - ]: 15028952 : Assert(entry->data.lockmode == BUFFER_LOCK_UNLOCK);
5770 : :
5771 : : /*
5772 : : * Lock out cancel/die interrupts until we exit the code section protected
5773 : : * by the content lock. This ensures that interrupts will not interfere
5774 : : * with manipulations of data structures in shared memory.
5775 : : */
5776 : 15028952 : HOLD_INTERRUPTS();
5777 : :
5778 : 15030750 : for (;;)
5779 : : {
5780 : 15030750 : uint32 wait_event = 0; /* initialized to avoid compiler warning */
5781 : 15030750 : bool mustwait;
5782 : :
5783 : : /*
5784 : : * Try to grab the lock the first time, we're not in the waitqueue
5785 : : * yet/anymore.
5786 : : */
5787 : 15030750 : mustwait = BufferLockAttempt(buf_hdr, mode);
5788 : :
5789 [ + + ]: 15030750 : if (likely(!mustwait))
5790 : : {
5791 : 15028808 : break;
5792 : : }
5793 : :
5794 : : /*
5795 : : * Ok, at this point we couldn't grab the lock on the first try. We
5796 : : * cannot simply queue ourselves to the end of the list and wait to be
5797 : : * woken up because by now the lock could long have been released.
5798 : : * Instead add us to the queue and try to grab the lock again. If we
5799 : : * succeed we need to revert the queuing and be happy, otherwise we
5800 : : * recheck the lock. If we still couldn't grab it, we know that the
5801 : : * other locker will see our queue entries when releasing since they
5802 : : * existed before we checked for the lock.
5803 : : */
5804 : :
5805 : : /* add to the queue */
5806 : 1942 : BufferLockQueueSelf(buf_hdr, mode);
5807 : :
5808 : : /* we're now guaranteed to be woken up if necessary */
5809 : 1942 : mustwait = BufferLockAttempt(buf_hdr, mode);
5810 : :
5811 : : /* ok, grabbed the lock the second time round, need to undo queueing */
5812 [ + + ]: 1942 : if (!mustwait)
5813 : : {
5814 : 144 : BufferLockDequeueSelf(buf_hdr);
5815 : 144 : break;
5816 : : }
5817 : :
5818 [ - + - - : 1798 : switch (mode)
+ ]
5819 : : {
5820 : : case BUFFER_LOCK_EXCLUSIVE:
5821 : 1093 : wait_event = WAIT_EVENT_BUFFER_EXCLUSIVE;
5822 : 1093 : break;
5823 : : case BUFFER_LOCK_SHARE_EXCLUSIVE:
5824 : 0 : wait_event = WAIT_EVENT_BUFFER_SHARE_EXCLUSIVE;
5825 : 0 : break;
5826 : : case BUFFER_LOCK_SHARE:
5827 : 705 : wait_event = WAIT_EVENT_BUFFER_SHARED;
5828 : 705 : break;
5829 : : case BUFFER_LOCK_UNLOCK:
5830 : 0 : pg_unreachable();
5831 : :
5832 : : }
5833 : 1798 : pgstat_report_wait_start(wait_event);
5834 : :
5835 : : /*
5836 : : * Wait until awakened.
5837 : : *
5838 : : * It is possible that we get awakened for a reason other than being
5839 : : * signaled by BufferLockWakeup(). If so, loop back and wait again.
5840 : : * Once we've gotten the lock, re-increment the sema by the number of
5841 : : * additional signals received.
5842 : : */
5843 : 1798 : for (;;)
5844 : : {
5845 : 1798 : PGSemaphoreLock(MyProc->sem);
5846 [ - + ]: 1798 : if (MyProc->lwWaiting == LW_WS_NOT_WAITING)
5847 : 1798 : break;
5848 : 0 : extraWaits++;
5849 : : }
5850 : :
5851 : 1798 : pgstat_report_wait_end();
5852 : :
5853 : : /* Retrying, allow BufferLockRelease to release waiters again. */
5854 : 1798 : pg_atomic_fetch_and_u64(&buf_hdr->state, ~BM_LOCK_WAKE_IN_PROGRESS);
5855 [ + - + ]: 15030750 : }
5856 : :
5857 : : /* Remember that we now hold this lock */
5858 : 15028952 : entry->data.lockmode = mode;
5859 : :
5860 : : /*
5861 : : * Fix the process wait semaphore's count for any absorbed wakeups.
5862 : : */
5863 [ - + ]: 15028952 : while (unlikely(extraWaits-- > 0))
5864 : 0 : PGSemaphoreUnlock(MyProc->sem);
5865 : 15028952 : }
5866 : :
5867 : : /*
5868 : : * Release a previously acquired buffer content lock.
5869 : : */
5870 : : static void
5871 : 15321271 : BufferLockUnlock(Buffer buffer, BufferDesc *buf_hdr)
5872 : : {
5873 : 15321271 : BufferLockMode mode;
5874 : 15321271 : uint64 oldstate;
5875 : 15321271 : uint64 sub;
5876 : :
5877 : 15321271 : mode = BufferLockDisownInternal(buffer, buf_hdr);
5878 : :
5879 : : /*
5880 : : * Release my hold on lock, after that it can immediately be acquired by
5881 : : * others, even if we still have to wakeup other waiters.
5882 : : */
5883 : 15321271 : sub = BufferLockReleaseSub(mode);
5884 : :
5885 : 15321271 : oldstate = pg_atomic_sub_fetch_u64(&buf_hdr->state, sub);
5886 : :
5887 : 15321271 : BufferLockProcessRelease(buf_hdr, mode, oldstate);
5888 : :
5889 : : /*
5890 : : * Now okay to allow cancel/die interrupts.
5891 : : */
5892 [ + - ]: 15321271 : RESUME_INTERRUPTS();
5893 : 15321271 : }
5894 : :
5895 : :
5896 : : /*
5897 : : * Acquire the content lock for the buffer, but only if we don't have to wait.
5898 : : */
5899 : : static bool
5900 : 292325 : BufferLockConditional(Buffer buffer, BufferDesc *buf_hdr, BufferLockMode mode)
5901 : : {
5902 : 292325 : PrivateRefCountEntry *entry = GetPrivateRefCountEntry(buffer, true);
5903 : 292325 : bool mustwait;
5904 : :
5905 : : /*
5906 : : * We better not already hold a lock on the buffer.
5907 : : */
5908 [ + - ]: 292325 : Assert(entry->data.lockmode == BUFFER_LOCK_UNLOCK);
5909 : :
5910 : : /*
5911 : : * Lock out cancel/die interrupts until we exit the code section protected
5912 : : * by the content lock. This ensures that interrupts will not interfere
5913 : : * with manipulations of data structures in shared memory.
5914 : : */
5915 : 292325 : HOLD_INTERRUPTS();
5916 : :
5917 : : /* Check for the lock */
5918 : 292325 : mustwait = BufferLockAttempt(buf_hdr, mode);
5919 : :
5920 [ + + ]: 292325 : if (mustwait)
5921 : : {
5922 : : /* Failed to get lock, so release interrupt holdoff */
5923 [ + - ]: 6 : RESUME_INTERRUPTS();
5924 : 6 : }
5925 : : else
5926 : : {
5927 : 292319 : entry->data.lockmode = mode;
5928 : : }
5929 : :
5930 : 584650 : return !mustwait;
5931 : 292325 : }
5932 : :
5933 : : /*
5934 : : * Internal function that tries to atomically acquire the content lock in the
5935 : : * passed in mode.
5936 : : *
5937 : : * This function will not block waiting for a lock to become free - that's the
5938 : : * caller's job.
5939 : : *
5940 : : * Similar to LWLockAttemptLock().
5941 : : */
5942 : : static inline bool
5943 : 15325017 : BufferLockAttempt(BufferDesc *buf_hdr, BufferLockMode mode)
5944 : : {
5945 : 15325017 : uint64 old_state;
5946 : :
5947 : : /*
5948 : : * Read once outside the loop, later iterations will get the newer value
5949 : : * via compare & exchange.
5950 : : */
5951 : 15325017 : old_state = pg_atomic_read_u64(&buf_hdr->state);
5952 : :
5953 : : /* loop until we've determined whether we could acquire the lock or not */
5954 : 15333366 : while (true)
5955 : : {
5956 : 15333366 : uint64 desired_state;
5957 : 15333366 : bool lock_free;
5958 : :
5959 : 15333366 : desired_state = old_state;
5960 : :
5961 [ + + ]: 15333366 : if (mode == BUFFER_LOCK_EXCLUSIVE)
5962 : : {
5963 : 4238184 : lock_free = (old_state & BM_LOCK_MASK) == 0;
5964 [ + + ]: 4238184 : if (lock_free)
5965 : 4235819 : desired_state += BM_LOCK_VAL_EXCLUSIVE;
5966 : 4238184 : }
5967 [ - + ]: 11095182 : else if (mode == BUFFER_LOCK_SHARE_EXCLUSIVE)
5968 : : {
5969 : 0 : lock_free = (old_state & (BM_LOCK_VAL_EXCLUSIVE | BM_LOCK_VAL_SHARE_EXCLUSIVE)) == 0;
5970 [ # # ]: 0 : if (lock_free)
5971 : 0 : desired_state += BM_LOCK_VAL_SHARE_EXCLUSIVE;
5972 : 0 : }
5973 : : else
5974 : : {
5975 : 11095182 : lock_free = (old_state & BM_LOCK_VAL_EXCLUSIVE) == 0;
5976 [ + + ]: 11095182 : if (lock_free)
5977 : 11093690 : desired_state += BM_LOCK_VAL_SHARED;
5978 : : }
5979 : :
5980 : : /*
5981 : : * Attempt to swap in the state we are expecting. If we didn't see
5982 : : * lock to be free, that's just the old value. If we saw it as free,
5983 : : * we'll attempt to mark it acquired. The reason that we always swap
5984 : : * in the value is that this doubles as a memory barrier. We could try
5985 : : * to be smarter and only swap in values if we saw the lock as free,
5986 : : * but benchmark haven't shown it as beneficial so far.
5987 : : *
5988 : : * Retry if the value changed since we last looked at it.
5989 : : */
5990 [ + + ]: 15333366 : if (likely(pg_atomic_compare_exchange_u64(&buf_hdr->state,
5991 : : &old_state, desired_state)))
5992 : : {
5993 [ + + ]: 15325017 : if (lock_free)
5994 : : {
5995 : : /* Great! Got the lock. */
5996 : 15321271 : return false;
5997 : : }
5998 : : else
5999 : 3746 : return true; /* somebody else has the lock */
6000 : : }
6001 [ + + ]: 15333366 : }
6002 : :
6003 : : pg_unreachable();
6004 : 15325017 : }
6005 : :
6006 : : /*
6007 : : * Add ourselves to the end of the content lock's wait queue.
6008 : : */
6009 : : static void
6010 : 1942 : BufferLockQueueSelf(BufferDesc *buf_hdr, BufferLockMode mode)
6011 : : {
6012 : : /*
6013 : : * If we don't have a PGPROC structure, there's no way to wait. This
6014 : : * should never occur, since MyProc should only be null during shared
6015 : : * memory initialization.
6016 : : */
6017 [ + - ]: 1942 : if (MyProc == NULL)
6018 [ # # # # ]: 0 : elog(PANIC, "cannot wait without a PGPROC structure");
6019 : :
6020 [ + - ]: 1942 : if (MyProc->lwWaiting != LW_WS_NOT_WAITING)
6021 [ # # # # ]: 0 : elog(PANIC, "queueing for lock while waiting on another one");
6022 : :
6023 : 1942 : LockBufHdr(buf_hdr);
6024 : :
6025 : : /* setting the flag is protected by the spinlock */
6026 : 1942 : pg_atomic_fetch_or_u64(&buf_hdr->state, BM_LOCK_HAS_WAITERS);
6027 : :
6028 : : /*
6029 : : * These are currently used both for lwlocks and buffer content locks,
6030 : : * which is acceptable, although not pretty, because a backend can't wait
6031 : : * for both types of locks at the same time.
6032 : : */
6033 : 1942 : MyProc->lwWaiting = LW_WS_WAITING;
6034 : 1942 : MyProc->lwWaitMode = mode;
6035 : :
6036 : 1942 : proclist_push_tail(&buf_hdr->lock_waiters, MyProcNumber, lwWaitLink);
6037 : :
6038 : : /* Can release the mutex now */
6039 : 1942 : UnlockBufHdr(buf_hdr);
6040 : 1942 : }
6041 : :
6042 : : /*
6043 : : * Remove ourselves from the waitlist.
6044 : : *
6045 : : * This is used if we queued ourselves because we thought we needed to sleep
6046 : : * but, after further checking, we discovered that we don't actually need to
6047 : : * do so.
6048 : : */
6049 : : static void
6050 : 144 : BufferLockDequeueSelf(BufferDesc *buf_hdr)
6051 : : {
6052 : 144 : bool on_waitlist;
6053 : :
6054 : 144 : LockBufHdr(buf_hdr);
6055 : :
6056 : 144 : on_waitlist = MyProc->lwWaiting == LW_WS_WAITING;
6057 [ + + ]: 144 : if (on_waitlist)
6058 : 121 : proclist_delete(&buf_hdr->lock_waiters, MyProcNumber, lwWaitLink);
6059 : :
6060 [ + + + + ]: 144 : if (proclist_is_empty(&buf_hdr->lock_waiters) &&
6061 : 142 : (pg_atomic_read_u64(&buf_hdr->state) & BM_LOCK_HAS_WAITERS) != 0)
6062 : : {
6063 : 119 : pg_atomic_fetch_and_u64(&buf_hdr->state, ~BM_LOCK_HAS_WAITERS);
6064 : 119 : }
6065 : :
6066 : : /* XXX: combine with fetch_and above? */
6067 : 144 : UnlockBufHdr(buf_hdr);
6068 : :
6069 : : /* clear waiting state again, nice for debugging */
6070 [ + + ]: 144 : if (on_waitlist)
6071 : 121 : MyProc->lwWaiting = LW_WS_NOT_WAITING;
6072 : : else
6073 : : {
6074 : 23 : int extraWaits = 0;
6075 : :
6076 : :
6077 : : /*
6078 : : * Somebody else dequeued us and has or will wake us up. Deal with the
6079 : : * superfluous absorption of a wakeup.
6080 : : */
6081 : :
6082 : : /*
6083 : : * Clear BM_LOCK_WAKE_IN_PROGRESS if somebody woke us before we
6084 : : * removed ourselves - they'll have set it.
6085 : : */
6086 : 23 : pg_atomic_fetch_and_u64(&buf_hdr->state, ~BM_LOCK_WAKE_IN_PROGRESS);
6087 : :
6088 : : /*
6089 : : * Now wait for the scheduled wakeup, otherwise our ->lwWaiting would
6090 : : * get reset at some inconvenient point later. Most of the time this
6091 : : * will immediately return.
6092 : : */
6093 : 23 : for (;;)
6094 : : {
6095 : 23 : PGSemaphoreLock(MyProc->sem);
6096 [ + - ]: 23 : if (MyProc->lwWaiting == LW_WS_NOT_WAITING)
6097 : 23 : break;
6098 : 0 : extraWaits++;
6099 : : }
6100 : :
6101 : : /*
6102 : : * Fix the process wait semaphore's count for any absorbed wakeups.
6103 : : */
6104 [ - + ]: 23 : while (extraWaits-- > 0)
6105 : 0 : PGSemaphoreUnlock(MyProc->sem);
6106 : 23 : }
6107 : 144 : }
6108 : :
6109 : : /*
6110 : : * Stop treating lock as held by current backend.
6111 : : *
6112 : : * After calling this function it's the callers responsibility to ensure that
6113 : : * the lock gets released, even in case of an error. This only is desirable if
6114 : : * the lock is going to be released in a different process than the process
6115 : : * that acquired it.
6116 : : */
6117 : : static inline void
6118 : 0 : BufferLockDisown(Buffer buffer, BufferDesc *buf_hdr)
6119 : : {
6120 : 0 : BufferLockDisownInternal(buffer, buf_hdr);
6121 [ # # ]: 0 : RESUME_INTERRUPTS();
6122 : 0 : }
6123 : :
6124 : : /*
6125 : : * Stop treating lock as held by current backend.
6126 : : *
6127 : : * This is the code that can be shared between actually releasing a lock
6128 : : * (BufferLockUnlock()) and just not tracking ownership of the lock anymore
6129 : : * without releasing the lock (BufferLockDisown()).
6130 : : */
6131 : : static inline int
6132 : 15321271 : BufferLockDisownInternal(Buffer buffer, BufferDesc *buf_hdr)
6133 : : {
6134 : 15321271 : BufferLockMode mode;
6135 : 15321271 : PrivateRefCountEntry *ref;
6136 : :
6137 : 15321271 : ref = GetPrivateRefCountEntry(buffer, false);
6138 [ + - ]: 15321271 : if (ref == NULL)
6139 [ # # # # ]: 0 : elog(ERROR, "lock %d is not held", buffer);
6140 : 15321271 : mode = ref->data.lockmode;
6141 : 15321271 : ref->data.lockmode = BUFFER_LOCK_UNLOCK;
6142 : :
6143 : 30642542 : return mode;
6144 : 15321271 : }
6145 : :
6146 : : /*
6147 : : * Wakeup all the lockers that currently have a chance to acquire the lock.
6148 : : *
6149 : : * wake_exclusive indicates whether exclusive lock waiters should be woken up.
6150 : : */
6151 : : static void
6152 : 1814 : BufferLockWakeup(BufferDesc *buf_hdr, bool wake_exclusive)
6153 : : {
6154 : 1814 : bool new_wake_in_progress = false;
6155 : 1814 : bool wake_share_exclusive = true;
6156 : 1814 : proclist_head wakeup;
6157 : 1814 : proclist_mutable_iter iter;
6158 : :
6159 : 1814 : proclist_init(&wakeup);
6160 : :
6161 : : /* lock wait list while collecting backends to wake up */
6162 : 1814 : LockBufHdr(buf_hdr);
6163 : :
6164 [ + + + + : 2557 : proclist_foreach_modify(iter, &buf_hdr->lock_waiters, lwWaitLink)
+ + ]
6165 : : {
6166 : 1846 : PGPROC *waiter = GetPGProcByNumber(iter.cur);
6167 : :
6168 : : /*
6169 : : * Already woke up a conflicting lock, so skip over this wait list
6170 : : * entry.
6171 : : */
6172 [ + + + + ]: 1846 : if (!wake_exclusive && waiter->lwWaitMode == BUFFER_LOCK_EXCLUSIVE)
6173 : 26 : continue;
6174 [ - + # # ]: 1820 : if (!wake_share_exclusive && waiter->lwWaitMode == BUFFER_LOCK_SHARE_EXCLUSIVE)
6175 : 0 : continue;
6176 : :
6177 : 1820 : proclist_delete(&buf_hdr->lock_waiters, iter.cur, lwWaitLink);
6178 : 1820 : proclist_push_tail(&wakeup, iter.cur, lwWaitLink);
6179 : :
6180 : : /*
6181 : : * Prevent additional wakeups until retryer gets to run. Backends that
6182 : : * are just waiting for the lock to become free don't retry
6183 : : * automatically.
6184 : : */
6185 : 1820 : new_wake_in_progress = true;
6186 : :
6187 : : /*
6188 : : * Signal that the process isn't on the wait list anymore. This allows
6189 : : * BufferLockDequeueSelf() to remove itself from the waitlist with a
6190 : : * proclist_delete(), rather than having to check if it has been
6191 : : * removed from the list.
6192 : : */
6193 [ + - ]: 1820 : Assert(waiter->lwWaiting == LW_WS_WAITING);
6194 : 1820 : waiter->lwWaiting = LW_WS_PENDING_WAKEUP;
6195 : :
6196 : : /*
6197 : : * Don't wakeup further waiters after waking a conflicting waiter.
6198 : : */
6199 [ + + ]: 1820 : if (waiter->lwWaitMode == BUFFER_LOCK_SHARE)
6200 : : {
6201 : : /*
6202 : : * Share locks conflict with exclusive locks.
6203 : : */
6204 : 717 : wake_exclusive = false;
6205 : 717 : }
6206 [ - + ]: 1103 : else if (waiter->lwWaitMode == BUFFER_LOCK_SHARE_EXCLUSIVE)
6207 : : {
6208 : : /*
6209 : : * Share-exclusive locks conflict with share-exclusive and
6210 : : * exclusive locks.
6211 : : */
6212 : 0 : wake_exclusive = false;
6213 : 0 : wake_share_exclusive = false;
6214 : 0 : }
6215 [ + - ]: 1103 : else if (waiter->lwWaitMode == BUFFER_LOCK_EXCLUSIVE)
6216 : : {
6217 : : /*
6218 : : * Exclusive locks conflict with all other locks, there's no point
6219 : : * in waking up anybody else.
6220 : : */
6221 : 1103 : break;
6222 : : }
6223 [ - + + + ]: 1846 : }
6224 : :
6225 [ + + + - ]: 1814 : Assert(proclist_is_empty(&wakeup) || pg_atomic_read_u64(&buf_hdr->state) & BM_LOCK_HAS_WAITERS);
6226 : :
6227 : : /* unset required flags, and release lock, in one fell swoop */
6228 : : {
6229 : 1814 : uint64 old_state;
6230 : 1814 : uint64 desired_state;
6231 : :
6232 : 1814 : old_state = pg_atomic_read_u64(&buf_hdr->state);
6233 : 1817 : while (true)
6234 : : {
6235 : 1817 : desired_state = old_state;
6236 : :
6237 : : /* compute desired flags */
6238 : :
6239 [ + + ]: 1817 : if (new_wake_in_progress)
6240 : 1766 : desired_state |= BM_LOCK_WAKE_IN_PROGRESS;
6241 : : else
6242 : 51 : desired_state &= ~BM_LOCK_WAKE_IN_PROGRESS;
6243 : :
6244 [ + + ]: 1817 : if (proclist_is_empty(&buf_hdr->lock_waiters))
6245 : 1723 : desired_state &= ~BM_LOCK_HAS_WAITERS;
6246 : :
6247 : 1817 : desired_state &= ~BM_LOCKED; /* release lock */
6248 : :
6249 [ + + + + ]: 3634 : if (pg_atomic_compare_exchange_u64(&buf_hdr->state, &old_state,
6250 : 1817 : desired_state))
6251 : 1814 : break;
6252 : : }
6253 : 1814 : }
6254 : :
6255 : : /* Awaken any waiters I removed from the queue. */
6256 [ + + + + : 3634 : proclist_foreach_modify(iter, &wakeup, lwWaitLink)
+ + ]
6257 : : {
6258 : 1820 : PGPROC *waiter = GetPGProcByNumber(iter.cur);
6259 : :
6260 : 1820 : proclist_delete(&wakeup, iter.cur, lwWaitLink);
6261 : :
6262 : : /*
6263 : : * Guarantee that lwWaiting being unset only becomes visible once the
6264 : : * unlink from the link has completed. Otherwise the target backend
6265 : : * could be woken up for other reason and enqueue for a new lock - if
6266 : : * that happens before the list unlink happens, the list would end up
6267 : : * being corrupted.
6268 : : *
6269 : : * The barrier pairs with the LockBufHdr() when enqueuing for another
6270 : : * lock.
6271 : : */
6272 : 1820 : pg_write_barrier();
6273 : 1820 : waiter->lwWaiting = LW_WS_NOT_WAITING;
6274 : 1820 : PGSemaphoreUnlock(waiter->sem);
6275 : 1820 : }
6276 : 1814 : }
6277 : :
6278 : : /*
6279 : : * Compute subtraction from buffer state for a release of a held lock in
6280 : : * `mode`.
6281 : : *
6282 : : * This is separated from BufferLockUnlock() as we want to combine the lock
6283 : : * release with other atomic operations when possible, leading to the lock
6284 : : * release being done in multiple places, each needing to compute what to
6285 : : * subtract from the lock state.
6286 : : */
6287 : : static inline uint64
6288 : 15321271 : BufferLockReleaseSub(BufferLockMode mode)
6289 : : {
6290 : : /*
6291 : : * Turns out that a switch() leads gcc to generate sufficiently worse code
6292 : : * for this to show up in profiles...
6293 : : */
6294 [ + + ]: 15321271 : if (mode == BUFFER_LOCK_EXCLUSIVE)
6295 : 4235715 : return BM_LOCK_VAL_EXCLUSIVE;
6296 [ - + ]: 11085556 : else if (mode == BUFFER_LOCK_SHARE_EXCLUSIVE)
6297 : 0 : return BM_LOCK_VAL_SHARE_EXCLUSIVE;
6298 : : else
6299 : : {
6300 [ + - ]: 11085556 : Assert(mode == BUFFER_LOCK_SHARE);
6301 : 11085556 : return BM_LOCK_VAL_SHARED;
6302 : : }
6303 : :
6304 : : return 0; /* keep compiler quiet */
6305 : 15321271 : }
6306 : :
6307 : : /*
6308 : : * Handle work that needs to be done after releasing a lock that was held in
6309 : : * `mode`, where `lockstate` is the result of the atomic operation modifying
6310 : : * the state variable.
6311 : : *
6312 : : * This is separated from BufferLockUnlock() as we want to combine the lock
6313 : : * release with other atomic operations when possible, leading to the lock
6314 : : * release being done in multiple places.
6315 : : */
6316 : : static void
6317 : 15321271 : BufferLockProcessRelease(BufferDesc *buf_hdr, BufferLockMode mode, uint64 lockstate)
6318 : : {
6319 : 15321271 : bool check_waiters = false;
6320 : 15321271 : bool wake_exclusive = false;
6321 : :
6322 : : /* nobody else can have that kind of lock */
6323 [ + - ]: 15321271 : Assert(!(lockstate & BM_LOCK_VAL_EXCLUSIVE));
6324 : :
6325 : : /*
6326 : : * If we're still waiting for backends to get scheduled, don't wake them
6327 : : * up again. Otherwise check if we need to look through the waitqueue to
6328 : : * wake other backends.
6329 : : */
6330 [ + + + + ]: 15321271 : if ((lockstate & BM_LOCK_HAS_WAITERS) &&
6331 : 2529 : !(lockstate & BM_LOCK_WAKE_IN_PROGRESS))
6332 : : {
6333 [ + + ]: 1825 : if ((lockstate & BM_LOCK_MASK) == 0)
6334 : : {
6335 : : /*
6336 : : * We released a lock and the lock was, in that moment, free. We
6337 : : * therefore can wake waiters for any kind of lock.
6338 : : */
6339 : 1814 : check_waiters = true;
6340 : 1814 : wake_exclusive = true;
6341 : 1814 : }
6342 [ + - ]: 11 : else if (mode == BUFFER_LOCK_SHARE_EXCLUSIVE)
6343 : : {
6344 : : /*
6345 : : * We released the lock, but another backend still holds a lock.
6346 : : * We can't have released an exclusive lock, as there couldn't
6347 : : * have been other lock holders. If we released a share lock, no
6348 : : * waiters need to be woken up, as there must be other share
6349 : : * lockers. However, if we held a share-exclusive lock, another
6350 : : * backend now could acquire a share-exclusive lock.
6351 : : */
6352 : 0 : check_waiters = true;
6353 : 0 : wake_exclusive = false;
6354 : 0 : }
6355 : 1825 : }
6356 : :
6357 : : /*
6358 : : * As waking up waiters requires the spinlock to be acquired, only do so
6359 : : * if necessary.
6360 : : */
6361 [ + + ]: 15321271 : if (check_waiters)
6362 : 1814 : BufferLockWakeup(buf_hdr, wake_exclusive);
6363 : 15321271 : }
6364 : :
6365 : : /*
6366 : : * BufferLockHeldByMeInMode - test whether my process holds the content lock
6367 : : * in the specified mode
6368 : : *
6369 : : * This is meant as debug support only.
6370 : : */
6371 : : static bool
6372 : 8621085 : BufferLockHeldByMeInMode(BufferDesc *buf_hdr, BufferLockMode mode)
6373 : : {
6374 : 17242170 : PrivateRefCountEntry *entry =
6375 : 8621085 : GetPrivateRefCountEntry(BufferDescriptorGetBuffer(buf_hdr), false);
6376 : :
6377 [ + - ]: 8621085 : if (!entry)
6378 : 0 : return false;
6379 : : else
6380 : 8621085 : return entry->data.lockmode == mode;
6381 : 8621085 : }
6382 : :
6383 : : /*
6384 : : * BufferLockHeldByMe - test whether my process holds the content lock in any
6385 : : * mode
6386 : : *
6387 : : * This is meant as debug support only.
6388 : : */
6389 : : static bool
6390 : 12503938 : BufferLockHeldByMe(BufferDesc *buf_hdr)
6391 : : {
6392 : 25007876 : PrivateRefCountEntry *entry =
6393 : 12503938 : GetPrivateRefCountEntry(BufferDescriptorGetBuffer(buf_hdr), false);
6394 : :
6395 [ + - ]: 12503938 : if (!entry)
6396 : 0 : return false;
6397 : : else
6398 : 12503938 : return entry->data.lockmode != BUFFER_LOCK_UNLOCK;
6399 : 12503938 : }
6400 : :
6401 : : /*
6402 : : * Release the content lock for the buffer.
6403 : : */
6404 : : void
6405 : 16875395 : UnlockBuffer(Buffer buffer)
6406 : : {
6407 : 16875395 : BufferDesc *buf_hdr;
6408 : :
6409 [ - + # # : 16875395 : Assert(BufferIsPinned(buffer));
+ + ]
6410 [ + + ]: 16875395 : if (BufferIsLocal(buffer))
6411 : 1561126 : return; /* local buffers need no lock */
6412 : :
6413 : 15314269 : buf_hdr = GetBufferDescriptor(buffer - 1);
6414 : 15314269 : BufferLockUnlock(buffer, buf_hdr);
6415 [ - + ]: 16875395 : }
6416 : :
6417 : : /*
6418 : : * Acquire the content_lock for the buffer.
6419 : : */
6420 : : void
6421 : 16558148 : LockBufferInternal(Buffer buffer, BufferLockMode mode)
6422 : : {
6423 : 16558148 : BufferDesc *buf_hdr;
6424 : :
6425 : : /*
6426 : : * We can't wait if we haven't got a PGPROC. This should only occur
6427 : : * during bootstrap or shared memory initialization. Put an Assert here
6428 : : * to catch unsafe coding practices.
6429 : : */
6430 [ - + # # ]: 16558148 : Assert(!(MyProc == NULL && IsUnderPostmaster));
6431 : :
6432 : : /* handled in LockBuffer() wrapper */
6433 [ + - ]: 16558148 : Assert(mode != BUFFER_LOCK_UNLOCK);
6434 : :
6435 [ + - # # : 16558148 : Assert(BufferIsPinned(buffer));
+ + ]
6436 [ + + ]: 16558148 : if (BufferIsLocal(buffer))
6437 : 1536194 : return; /* local buffers need no lock */
6438 : :
6439 : 15021954 : buf_hdr = GetBufferDescriptor(buffer - 1);
6440 : :
6441 : : /*
6442 : : * Test the most frequent lock modes first. While a switch (mode) would be
6443 : : * nice, at least gcc generates considerably worse code for it.
6444 : : *
6445 : : * Call BufferLockAcquire() with a constant argument for mode, to generate
6446 : : * more efficient code for the different lock modes.
6447 : : */
6448 [ + + ]: 15021954 : if (mode == BUFFER_LOCK_SHARE)
6449 : 11078558 : BufferLockAcquire(buffer, buf_hdr, BUFFER_LOCK_SHARE);
6450 [ + - ]: 3943396 : else if (mode == BUFFER_LOCK_EXCLUSIVE)
6451 : 3943396 : BufferLockAcquire(buffer, buf_hdr, BUFFER_LOCK_EXCLUSIVE);
6452 [ # # ]: 0 : else if (mode == BUFFER_LOCK_SHARE_EXCLUSIVE)
6453 : 0 : BufferLockAcquire(buffer, buf_hdr, BUFFER_LOCK_SHARE_EXCLUSIVE);
6454 : : else
6455 [ # # # # ]: 0 : elog(ERROR, "unrecognized buffer lock mode: %d", mode);
6456 [ - + ]: 16558148 : }
6457 : :
6458 : : /*
6459 : : * Acquire the content_lock for the buffer, but only if we don't have to wait.
6460 : : *
6461 : : * This assumes the caller wants BUFFER_LOCK_EXCLUSIVE mode.
6462 : : */
6463 : : bool
6464 : 313908 : ConditionalLockBuffer(Buffer buffer)
6465 : : {
6466 : 313908 : BufferDesc *buf;
6467 : :
6468 [ - + # # : 313908 : Assert(BufferIsPinned(buffer));
+ + ]
6469 [ + + ]: 313908 : if (BufferIsLocal(buffer))
6470 : 21583 : return true; /* act as though we got it */
6471 : :
6472 : 292325 : buf = GetBufferDescriptor(buffer - 1);
6473 : :
6474 : 292325 : return BufferLockConditional(buffer, buf, BUFFER_LOCK_EXCLUSIVE);
6475 : 313908 : }
6476 : :
6477 : : /*
6478 : : * Verify that this backend is pinning the buffer exactly once.
6479 : : *
6480 : : * NOTE: Like in BufferIsPinned(), what we check here is that *this* backend
6481 : : * holds a pin on the buffer. We do not care whether some other backend does.
6482 : : */
6483 : : void
6484 : 91527 : CheckBufferIsPinnedOnce(Buffer buffer)
6485 : : {
6486 [ + + ]: 91527 : if (BufferIsLocal(buffer))
6487 : : {
6488 [ + - ]: 258 : if (LocalRefCount[-buffer - 1] != 1)
6489 [ # # # # ]: 0 : elog(ERROR, "incorrect local pin count: %d",
6490 : : LocalRefCount[-buffer - 1]);
6491 : 258 : }
6492 : : else
6493 : : {
6494 [ + - ]: 91269 : if (GetPrivateRefCount(buffer) != 1)
6495 [ # # # # ]: 0 : elog(ERROR, "incorrect local pin count: %d",
6496 : : GetPrivateRefCount(buffer));
6497 : : }
6498 : 91527 : }
6499 : :
6500 : : /*
6501 : : * LockBufferForCleanup - lock a buffer in preparation for deleting items
6502 : : *
6503 : : * Items may be deleted from a disk page only when the caller (a) holds an
6504 : : * exclusive lock on the buffer and (b) has observed that no other backend
6505 : : * holds a pin on the buffer. If there is a pin, then the other backend
6506 : : * might have a pointer into the buffer (for example, a heapscan reference
6507 : : * to an item --- see README for more details). It's OK if a pin is added
6508 : : * after the cleanup starts, however; the newly-arrived backend will be
6509 : : * unable to look at the page until we release the exclusive lock.
6510 : : *
6511 : : * To implement this protocol, a would-be deleter must pin the buffer and
6512 : : * then call LockBufferForCleanup(). LockBufferForCleanup() is similar to
6513 : : * LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE), except that it loops until
6514 : : * it has successfully observed pin count = 1.
6515 : : */
6516 : : void
6517 : 766 : LockBufferForCleanup(Buffer buffer)
6518 : : {
6519 : 766 : BufferDesc *bufHdr;
6520 : 766 : TimestampTz waitStart = 0;
6521 : 766 : bool waiting = false;
6522 : 766 : bool logged_recovery_conflict = false;
6523 : :
6524 [ - + # # : 766 : Assert(BufferIsPinned(buffer));
+ + ]
6525 [ + - ]: 766 : Assert(PinCountWaitBuf == NULL);
6526 : :
6527 : 766 : CheckBufferIsPinnedOnce(buffer);
6528 : :
6529 : : /*
6530 : : * We do not yet need to be worried about in-progress AIOs holding a pin,
6531 : : * as we, so far, only support doing reads via AIO and this function can
6532 : : * only be called once the buffer is valid (i.e. no read can be in
6533 : : * flight).
6534 : : */
6535 : :
6536 : : /* Nobody else to wait for */
6537 [ + + ]: 766 : if (BufferIsLocal(buffer))
6538 : 2 : return;
6539 : :
6540 : 764 : bufHdr = GetBufferDescriptor(buffer - 1);
6541 : :
6542 : 764 : for (;;)
6543 : : {
6544 : 764 : uint64 buf_state;
6545 : 764 : uint64 unset_bits = 0;
6546 : :
6547 : : /* Try to acquire lock */
6548 : 764 : LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
6549 : 764 : buf_state = LockBufHdr(bufHdr);
6550 : :
6551 [ + - ]: 764 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
6552 [ + - ]: 764 : if (BUF_STATE_GET_REFCOUNT(buf_state) == 1)
6553 : : {
6554 : : /* Successfully acquired exclusive lock with pincount 1 */
6555 : 764 : UnlockBufHdr(bufHdr);
6556 : :
6557 : : /*
6558 : : * Emit the log message if recovery conflict on buffer pin was
6559 : : * resolved but the startup process waited longer than
6560 : : * deadlock_timeout for it.
6561 : : */
6562 [ + - ]: 764 : if (logged_recovery_conflict)
6563 : 0 : LogRecoveryConflict(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN,
6564 : 0 : waitStart, GetCurrentTimestamp(),
6565 : : NULL, false);
6566 : :
6567 [ + - ]: 764 : if (waiting)
6568 : : {
6569 : : /* reset ps display to remove the suffix if we added one */
6570 : 0 : set_ps_display_remove_suffix();
6571 : 0 : waiting = false;
6572 : 0 : }
6573 : 764 : return;
6574 : : }
6575 : : /* Failed, so mark myself as waiting for pincount 1 */
6576 [ # # ]: 0 : if (buf_state & BM_PIN_COUNT_WAITER)
6577 : : {
6578 : 0 : UnlockBufHdr(bufHdr);
6579 : 0 : LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
6580 [ # # # # ]: 0 : elog(ERROR, "multiple backends attempting to wait for pincount 1");
6581 : 0 : }
6582 : 0 : bufHdr->wait_backend_pgprocno = MyProcNumber;
6583 : 0 : PinCountWaitBuf = bufHdr;
6584 : 0 : UnlockBufHdrExt(bufHdr, buf_state,
6585 : : BM_PIN_COUNT_WAITER, 0,
6586 : : 0);
6587 : 0 : LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
6588 : :
6589 : : /* Wait to be signaled by UnpinBuffer() */
6590 [ # # ]: 0 : if (InHotStandby)
6591 : : {
6592 [ # # ]: 0 : if (!waiting)
6593 : : {
6594 : : /* adjust the process title to indicate that it's waiting */
6595 : 0 : set_ps_display_suffix("waiting");
6596 : 0 : waiting = true;
6597 : 0 : }
6598 : :
6599 : : /*
6600 : : * Emit the log message if the startup process is waiting longer
6601 : : * than deadlock_timeout for recovery conflict on buffer pin.
6602 : : *
6603 : : * Skip this if first time through because the startup process has
6604 : : * not started waiting yet in this case. So, the wait start
6605 : : * timestamp is set after this logic.
6606 : : */
6607 [ # # # # ]: 0 : if (waitStart != 0 && !logged_recovery_conflict)
6608 : : {
6609 : 0 : TimestampTz now = GetCurrentTimestamp();
6610 : :
6611 [ # # # # ]: 0 : if (TimestampDifferenceExceeds(waitStart, now,
6612 : 0 : DeadlockTimeout))
6613 : : {
6614 : 0 : LogRecoveryConflict(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN,
6615 : 0 : waitStart, now, NULL, true);
6616 : 0 : logged_recovery_conflict = true;
6617 : 0 : }
6618 : 0 : }
6619 : :
6620 : : /*
6621 : : * Set the wait start timestamp if logging is enabled and first
6622 : : * time through.
6623 : : */
6624 [ # # # # ]: 0 : if (log_recovery_conflict_waits && waitStart == 0)
6625 : 0 : waitStart = GetCurrentTimestamp();
6626 : :
6627 : : /* Publish the bufid that Startup process waits on */
6628 : 0 : SetStartupBufferPinWaitBufId(buffer - 1);
6629 : : /* Set alarm and then wait to be signaled by UnpinBuffer() */
6630 : 0 : ResolveRecoveryConflictWithBufferPin();
6631 : : /* Reset the published bufid */
6632 : 0 : SetStartupBufferPinWaitBufId(-1);
6633 : 0 : }
6634 : : else
6635 : 0 : ProcWaitForSignal(WAIT_EVENT_BUFFER_CLEANUP);
6636 : :
6637 : : /*
6638 : : * Remove flag marking us as waiter. Normally this will not be set
6639 : : * anymore, but ProcWaitForSignal() can return for other signals as
6640 : : * well. We take care to only reset the flag if we're the waiter, as
6641 : : * theoretically another backend could have started waiting. That's
6642 : : * impossible with the current usages due to table level locking, but
6643 : : * better be safe.
6644 : : */
6645 : 0 : buf_state = LockBufHdr(bufHdr);
6646 [ # # # # ]: 0 : if ((buf_state & BM_PIN_COUNT_WAITER) != 0 &&
6647 : 0 : bufHdr->wait_backend_pgprocno == MyProcNumber)
6648 : 0 : unset_bits |= BM_PIN_COUNT_WAITER;
6649 : :
6650 : 0 : UnlockBufHdrExt(bufHdr, buf_state,
6651 : 0 : 0, unset_bits,
6652 : : 0);
6653 : :
6654 : 0 : PinCountWaitBuf = NULL;
6655 : : /* Loop back and try again */
6656 [ + - ]: 764 : }
6657 : 766 : }
6658 : :
6659 : : /*
6660 : : * Check called from ProcessRecoveryConflictInterrupts() when Startup process
6661 : : * requests cancellation of all pin holders that are blocking it.
6662 : : */
6663 : : bool
6664 : 0 : HoldingBufferPinThatDelaysRecovery(void)
6665 : : {
6666 : 0 : int bufid = GetStartupBufferPinWaitBufId();
6667 : :
6668 : : /*
6669 : : * If we get woken slowly then it's possible that the Startup process was
6670 : : * already woken by other backends before we got here. Also possible that
6671 : : * we get here by multiple interrupts or interrupts at inappropriate
6672 : : * times, so make sure we do nothing if the bufid is not set.
6673 : : */
6674 [ # # ]: 0 : if (bufid < 0)
6675 : 0 : return false;
6676 : :
6677 [ # # ]: 0 : if (GetPrivateRefCount(bufid + 1) > 0)
6678 : 0 : return true;
6679 : :
6680 : 0 : return false;
6681 : 0 : }
6682 : :
6683 : : /*
6684 : : * ConditionalLockBufferForCleanup - as above, but don't wait to get the lock
6685 : : *
6686 : : * We won't loop, but just check once to see if the pin count is OK. If
6687 : : * not, return false with no lock held.
6688 : : */
6689 : : bool
6690 : 15033 : ConditionalLockBufferForCleanup(Buffer buffer)
6691 : : {
6692 : 15033 : BufferDesc *bufHdr;
6693 : 15033 : uint64 buf_state,
6694 : : refcount;
6695 : :
6696 [ + - ]: 15033 : Assert(BufferIsValid(buffer));
6697 : :
6698 : : /* see AIO related comment in LockBufferForCleanup() */
6699 : :
6700 [ + + ]: 15033 : if (BufferIsLocal(buffer))
6701 : : {
6702 : 265 : refcount = LocalRefCount[-buffer - 1];
6703 : : /* There should be exactly one pin */
6704 [ + - ]: 265 : Assert(refcount > 0);
6705 [ + + ]: 265 : if (refcount != 1)
6706 : 7 : return false;
6707 : : /* Nobody else to wait for */
6708 : 258 : return true;
6709 : : }
6710 : :
6711 : : /* There should be exactly one local pin */
6712 : 14768 : refcount = GetPrivateRefCount(buffer);
6713 [ + - ]: 14768 : Assert(refcount);
6714 [ + + ]: 14768 : if (refcount != 1)
6715 : 32 : return false;
6716 : :
6717 : : /* Try to acquire lock */
6718 [ + + ]: 14736 : if (!ConditionalLockBuffer(buffer))
6719 : 6 : return false;
6720 : :
6721 : 14730 : bufHdr = GetBufferDescriptor(buffer - 1);
6722 : 14730 : buf_state = LockBufHdr(bufHdr);
6723 : 14730 : refcount = BUF_STATE_GET_REFCOUNT(buf_state);
6724 : :
6725 [ + - ]: 14730 : Assert(refcount > 0);
6726 [ + + ]: 14730 : if (refcount == 1)
6727 : : {
6728 : : /* Successfully acquired exclusive lock with pincount 1 */
6729 : 14722 : UnlockBufHdr(bufHdr);
6730 : 14722 : return true;
6731 : : }
6732 : :
6733 : : /* Failed, so release the lock */
6734 : 8 : UnlockBufHdr(bufHdr);
6735 : 8 : LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
6736 : 8 : return false;
6737 : 15033 : }
6738 : :
6739 : : /*
6740 : : * IsBufferCleanupOK - as above, but we already have the lock
6741 : : *
6742 : : * Check whether it's OK to perform cleanup on a buffer we've already
6743 : : * locked. If we observe that the pin count is 1, our exclusive lock
6744 : : * happens to be a cleanup lock, and we can proceed with anything that
6745 : : * would have been allowable had we sought a cleanup lock originally.
6746 : : */
6747 : : bool
6748 : 662 : IsBufferCleanupOK(Buffer buffer)
6749 : : {
6750 : 662 : BufferDesc *bufHdr;
6751 : 662 : uint64 buf_state;
6752 : :
6753 [ + - ]: 662 : Assert(BufferIsValid(buffer));
6754 : :
6755 : : /* see AIO related comment in LockBufferForCleanup() */
6756 : :
6757 [ + - ]: 662 : if (BufferIsLocal(buffer))
6758 : : {
6759 : : /* There should be exactly one pin */
6760 [ # # ]: 0 : if (LocalRefCount[-buffer - 1] != 1)
6761 : 0 : return false;
6762 : : /* Nobody else to wait for */
6763 : 0 : return true;
6764 : : }
6765 : :
6766 : : /* There should be exactly one local pin */
6767 [ - + ]: 662 : if (GetPrivateRefCount(buffer) != 1)
6768 : 0 : return false;
6769 : :
6770 : 662 : bufHdr = GetBufferDescriptor(buffer - 1);
6771 : :
6772 : : /* caller must hold exclusive lock on buffer */
6773 [ + - ]: 662 : Assert(BufferIsLockedByMeInMode(buffer, BUFFER_LOCK_EXCLUSIVE));
6774 : :
6775 : 662 : buf_state = LockBufHdr(bufHdr);
6776 : :
6777 [ + - ]: 662 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
6778 [ + - ]: 662 : if (BUF_STATE_GET_REFCOUNT(buf_state) == 1)
6779 : : {
6780 : : /* pincount is OK. */
6781 : 662 : UnlockBufHdr(bufHdr);
6782 : 662 : return true;
6783 : : }
6784 : :
6785 : 0 : UnlockBufHdr(bufHdr);
6786 : 0 : return false;
6787 : 662 : }
6788 : :
6789 : :
6790 : : /*
6791 : : * Functions for buffer I/O handling
6792 : : *
6793 : : * Also note that these are used only for shared buffers, not local ones.
6794 : : */
6795 : :
6796 : : /*
6797 : : * WaitIO -- Block until the IO_IN_PROGRESS flag on 'buf' is cleared.
6798 : : */
6799 : : static void
6800 : 1 : WaitIO(BufferDesc *buf)
6801 : : {
6802 : 1 : ConditionVariable *cv = BufferDescriptorGetIOCV(buf);
6803 : :
6804 : 1 : ConditionVariablePrepareToSleep(cv);
6805 : 2 : for (;;)
6806 : : {
6807 : 2 : uint64 buf_state;
6808 : 2 : PgAioWaitRef iow;
6809 : :
6810 : : /*
6811 : : * It may not be necessary to acquire the spinlock to check the flag
6812 : : * here, but since this test is essential for correctness, we'd better
6813 : : * play it safe.
6814 : : */
6815 : 2 : buf_state = LockBufHdr(buf);
6816 : :
6817 : : /*
6818 : : * Copy the wait reference while holding the spinlock. This protects
6819 : : * against a concurrent TerminateBufferIO() in another backend from
6820 : : * clearing the wref while it's being read.
6821 : : */
6822 : 2 : iow = buf->io_wref;
6823 : 2 : UnlockBufHdr(buf);
6824 : :
6825 : : /* no IO in progress, we don't need to wait */
6826 [ + + ]: 2 : if (!(buf_state & BM_IO_IN_PROGRESS))
6827 : 1 : break;
6828 : :
6829 : : /*
6830 : : * The buffer has asynchronous IO in progress, wait for it to
6831 : : * complete.
6832 : : */
6833 [ - + ]: 1 : if (pgaio_wref_valid(&iow))
6834 : : {
6835 : 0 : pgaio_wref_wait(&iow);
6836 : :
6837 : : /*
6838 : : * The AIO subsystem internally uses condition variables and thus
6839 : : * might remove this backend from the BufferDesc's CV. While that
6840 : : * wouldn't cause a correctness issue (the first CV sleep just
6841 : : * immediately returns if not already registered), it seems worth
6842 : : * avoiding unnecessary loop iterations, given that we take care
6843 : : * to do so at the start of the function.
6844 : : */
6845 : 0 : ConditionVariablePrepareToSleep(cv);
6846 : 0 : continue;
6847 : : }
6848 : :
6849 : : /* wait on BufferDesc->cv, e.g. for concurrent synchronous IO */
6850 : 1 : ConditionVariableSleep(cv, WAIT_EVENT_BUFFER_IO);
6851 [ - - + + ]: 2 : }
6852 : 1 : ConditionVariableCancelSleep();
6853 : 1 : }
6854 : :
6855 : : /*
6856 : : * StartBufferIO: begin I/O on this buffer
6857 : : * (Assumptions)
6858 : : * My process is executing no IO on this buffer
6859 : : * The buffer is Pinned
6860 : : *
6861 : : * In some scenarios multiple backends could attempt the same I/O operation
6862 : : * concurrently. If someone else has already started I/O on this buffer then
6863 : : * we will wait for completion of the IO using WaitIO().
6864 : : *
6865 : : * Input operations are only attempted on buffers that are not BM_VALID,
6866 : : * and output operations only on buffers that are BM_VALID and BM_DIRTY,
6867 : : * so we can always tell if the work is already done.
6868 : : *
6869 : : * Returns true if we successfully marked the buffer as I/O busy,
6870 : : * false if someone else already did the work.
6871 : : *
6872 : : * If nowait is true, then we don't wait for an I/O to be finished by another
6873 : : * backend. In that case, false indicates either that the I/O was already
6874 : : * finished, or is still in progress. This is useful for callers that want to
6875 : : * find out if they can perform the I/O as part of a larger operation, without
6876 : : * waiting for the answer or distinguishing the reasons why not.
6877 : : */
6878 : : bool
6879 : 47536 : StartBufferIO(BufferDesc *buf, bool forInput, bool nowait)
6880 : : {
6881 : 47536 : uint64 buf_state;
6882 : :
6883 : 47536 : ResourceOwnerEnlarge(CurrentResourceOwner);
6884 : :
6885 : 47537 : for (;;)
6886 : : {
6887 : 47537 : buf_state = LockBufHdr(buf);
6888 : :
6889 [ + + ]: 47537 : if (!(buf_state & BM_IO_IN_PROGRESS))
6890 : 47536 : break;
6891 : 1 : UnlockBufHdr(buf);
6892 [ - + ]: 1 : if (nowait)
6893 : 0 : return false;
6894 : 1 : WaitIO(buf);
6895 : : }
6896 : :
6897 : : /* Once we get here, there is definitely no I/O active on this buffer */
6898 : :
6899 : : /* Check if someone else already did the I/O */
6900 [ + + + + ]: 47536 : if (forInput ? (buf_state & BM_VALID) : !(buf_state & BM_DIRTY))
6901 : : {
6902 : 13995 : UnlockBufHdr(buf);
6903 : 13995 : return false;
6904 : : }
6905 : :
6906 : 47535 : UnlockBufHdrExt(buf, buf_state,
6907 : : BM_IO_IN_PROGRESS, 0,
6908 : : 0);
6909 : :
6910 : 95070 : ResourceOwnerRememberBufferIO(CurrentResourceOwner,
6911 : 47535 : BufferDescriptorGetBuffer(buf));
6912 : :
6913 : 47535 : return true;
6914 : 61530 : }
6915 : :
6916 : : /*
6917 : : * TerminateBufferIO: release a buffer we were doing I/O on
6918 : : * (Assumptions)
6919 : : * My process is executing IO for the buffer
6920 : : * BM_IO_IN_PROGRESS bit is set for the buffer
6921 : : * The buffer is Pinned
6922 : : *
6923 : : * If clear_dirty is true and BM_JUST_DIRTIED is not set, we clear the
6924 : : * buffer's BM_DIRTY flag. This is appropriate when terminating a
6925 : : * successful write. The check on BM_JUST_DIRTIED is necessary to avoid
6926 : : * marking the buffer clean if it was re-dirtied while we were writing.
6927 : : *
6928 : : * set_flag_bits gets ORed into the buffer's flags. It must include
6929 : : * BM_IO_ERROR in a failure case. For successful completion it could
6930 : : * be 0, or BM_VALID if we just finished reading in the page.
6931 : : *
6932 : : * If forget_owner is true, we release the buffer I/O from the current
6933 : : * resource owner. (forget_owner=false is used when the resource owner itself
6934 : : * is being released)
6935 : : */
6936 : : void
6937 : 46058 : TerminateBufferIO(BufferDesc *buf, bool clear_dirty, uint64 set_flag_bits,
6938 : : bool forget_owner, bool release_aio)
6939 : : {
6940 : 46058 : uint64 buf_state;
6941 : 46058 : uint64 unset_flag_bits = 0;
6942 : 46058 : int refcount_change = 0;
6943 : :
6944 : 46058 : buf_state = LockBufHdr(buf);
6945 : :
6946 [ + - ]: 46058 : Assert(buf_state & BM_IO_IN_PROGRESS);
6947 : 46058 : unset_flag_bits |= BM_IO_IN_PROGRESS;
6948 : :
6949 : : /* Clear earlier errors, if this IO failed, it'll be marked again */
6950 : 46058 : unset_flag_bits |= BM_IO_ERROR;
6951 : :
6952 [ + + - + ]: 46058 : if (clear_dirty && !(buf_state & BM_JUST_DIRTIED))
6953 : 6998 : unset_flag_bits |= BM_DIRTY | BM_CHECKPOINT_NEEDED;
6954 : :
6955 [ + + ]: 46058 : if (release_aio)
6956 : : {
6957 : : /* release ownership by the AIO subsystem */
6958 [ + - ]: 6904 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
6959 : 6904 : refcount_change = -1;
6960 : 6904 : pgaio_wref_clear(&buf->io_wref);
6961 : 6904 : }
6962 : :
6963 : 92116 : buf_state = UnlockBufHdrExt(buf, buf_state,
6964 : 46058 : set_flag_bits, unset_flag_bits,
6965 : 46058 : refcount_change);
6966 : :
6967 [ + + ]: 46058 : if (forget_owner)
6968 : 78308 : ResourceOwnerForgetBufferIO(CurrentResourceOwner,
6969 : 39154 : BufferDescriptorGetBuffer(buf));
6970 : :
6971 : 46058 : ConditionVariableBroadcast(BufferDescriptorGetIOCV(buf));
6972 : :
6973 : : /*
6974 : : * Support LockBufferForCleanup()
6975 : : *
6976 : : * We may have just released the last pin other than the waiter's. In most
6977 : : * cases, this backend holds another pin on the buffer. But, if, for
6978 : : * example, this backend is completing an IO issued by another backend, it
6979 : : * may be time to wake the waiter.
6980 : : */
6981 [ + + + - ]: 46058 : if (release_aio && (buf_state & BM_PIN_COUNT_WAITER))
6982 : 0 : WakePinCountWaiter(buf);
6983 : 46058 : }
6984 : :
6985 : : /*
6986 : : * AbortBufferIO: Clean up active buffer I/O after an error.
6987 : : *
6988 : : * All LWLocks & content locks we might have held have been released, but we
6989 : : * haven't yet released buffer pins, so the buffer is still pinned.
6990 : : *
6991 : : * If I/O was in progress, we always set BM_IO_ERROR, even though it's
6992 : : * possible the error condition wasn't related to the I/O.
6993 : : *
6994 : : * Note: this does not remove the buffer I/O from the resource owner.
6995 : : * That's correct when we're releasing the whole resource owner, but
6996 : : * beware if you use this in other contexts.
6997 : : */
6998 : : static void
6999 : 0 : AbortBufferIO(Buffer buffer)
7000 : : {
7001 : 0 : BufferDesc *buf_hdr = GetBufferDescriptor(buffer - 1);
7002 : 0 : uint64 buf_state;
7003 : :
7004 : 0 : buf_state = LockBufHdr(buf_hdr);
7005 [ # # ]: 0 : Assert(buf_state & (BM_IO_IN_PROGRESS | BM_TAG_VALID));
7006 : :
7007 [ # # ]: 0 : if (!(buf_state & BM_VALID))
7008 : : {
7009 [ # # ]: 0 : Assert(!(buf_state & BM_DIRTY));
7010 : 0 : UnlockBufHdr(buf_hdr);
7011 : 0 : }
7012 : : else
7013 : : {
7014 [ # # ]: 0 : Assert(buf_state & BM_DIRTY);
7015 : 0 : UnlockBufHdr(buf_hdr);
7016 : :
7017 : : /* Issue notice if this is not the first failure... */
7018 [ # # ]: 0 : if (buf_state & BM_IO_ERROR)
7019 : : {
7020 : : /* Buffer is pinned, so we can read tag without spinlock */
7021 [ # # # # ]: 0 : ereport(WARNING,
7022 : : (errcode(ERRCODE_IO_ERROR),
7023 : : errmsg("could not write block %u of %s",
7024 : : buf_hdr->tag.blockNum,
7025 : : relpathperm(BufTagGetRelFileLocator(&buf_hdr->tag),
7026 : : BufTagGetForkNum(&buf_hdr->tag)).str),
7027 : : errdetail("Multiple failures --- write error might be permanent.")));
7028 : 0 : }
7029 : : }
7030 : :
7031 : 0 : TerminateBufferIO(buf_hdr, false, BM_IO_ERROR, false, false);
7032 : 0 : }
7033 : :
7034 : : /*
7035 : : * Error context callback for errors occurring during shared buffer writes.
7036 : : */
7037 : : static void
7038 : 0 : shared_buffer_write_error_callback(void *arg)
7039 : : {
7040 : 0 : BufferDesc *bufHdr = (BufferDesc *) arg;
7041 : :
7042 : : /* Buffer is pinned, so we can read the tag without locking the spinlock */
7043 [ # # ]: 0 : if (bufHdr != NULL)
7044 : 0 : errcontext("writing block %u of relation \"%s\"",
7045 : 0 : bufHdr->tag.blockNum,
7046 : 0 : relpathperm(BufTagGetRelFileLocator(&bufHdr->tag),
7047 : 0 : BufTagGetForkNum(&bufHdr->tag)).str);
7048 : 0 : }
7049 : :
7050 : : /*
7051 : : * Error context callback for errors occurring during local buffer writes.
7052 : : */
7053 : : static void
7054 : 0 : local_buffer_write_error_callback(void *arg)
7055 : : {
7056 : 0 : BufferDesc *bufHdr = (BufferDesc *) arg;
7057 : :
7058 [ # # ]: 0 : if (bufHdr != NULL)
7059 : 0 : errcontext("writing block %u of relation \"%s\"",
7060 : 0 : bufHdr->tag.blockNum,
7061 : 0 : relpathbackend(BufTagGetRelFileLocator(&bufHdr->tag),
7062 : : MyProcNumber,
7063 : 0 : BufTagGetForkNum(&bufHdr->tag)).str);
7064 : 0 : }
7065 : :
7066 : : /*
7067 : : * RelFileLocator qsort/bsearch comparator; see RelFileLocatorEquals.
7068 : : */
7069 : : static int
7070 : 2573423 : rlocator_comparator(const void *p1, const void *p2)
7071 : : {
7072 : 2573423 : RelFileLocator n1 = *(const RelFileLocator *) p1;
7073 : 2573423 : RelFileLocator n2 = *(const RelFileLocator *) p2;
7074 : :
7075 [ + + ]: 2573423 : if (n1.relNumber < n2.relNumber)
7076 : 2559066 : return -1;
7077 [ + + ]: 14357 : else if (n1.relNumber > n2.relNumber)
7078 : 13819 : return 1;
7079 : :
7080 [ - + ]: 538 : if (n1.dbOid < n2.dbOid)
7081 : 0 : return -1;
7082 [ - + ]: 538 : else if (n1.dbOid > n2.dbOid)
7083 : 0 : return 1;
7084 : :
7085 [ - + ]: 538 : if (n1.spcOid < n2.spcOid)
7086 : 0 : return -1;
7087 [ - + ]: 538 : else if (n1.spcOid > n2.spcOid)
7088 : 0 : return 1;
7089 : : else
7090 : 538 : return 0;
7091 : 2573423 : }
7092 : :
7093 : : /*
7094 : : * Lock buffer header - set BM_LOCKED in buffer state.
7095 : : */
7096 : : uint64
7097 : 1279465 : LockBufHdr(BufferDesc *desc)
7098 : : {
7099 : 1279465 : uint64 old_buf_state;
7100 : :
7101 [ + - ]: 1279465 : Assert(!BufferIsLocal(BufferDescriptorGetBuffer(desc)));
7102 : :
7103 : 1279628 : while (true)
7104 : : {
7105 : : /*
7106 : : * Always try once to acquire the lock directly, without setting up
7107 : : * the spin-delay infrastructure. The work necessary for that shows up
7108 : : * in profiles and is rarely necessary.
7109 : : */
7110 : 1279628 : old_buf_state = pg_atomic_fetch_or_u64(&desc->state, BM_LOCKED);
7111 [ + + ]: 1279628 : if (likely(!(old_buf_state & BM_LOCKED)))
7112 : 1279465 : break; /* got lock */
7113 : :
7114 : : /* and then spin without atomic operations until lock is released */
7115 : : {
7116 : 163 : SpinDelayStatus delayStatus;
7117 : :
7118 : 163 : init_local_spin_delay(&delayStatus);
7119 : :
7120 [ + + ]: 576 : while (old_buf_state & BM_LOCKED)
7121 : : {
7122 : 413 : perform_spin_delay(&delayStatus);
7123 : 413 : old_buf_state = pg_atomic_read_u64(&desc->state);
7124 : : }
7125 : 163 : finish_spin_delay(&delayStatus);
7126 : 163 : }
7127 : :
7128 : : /*
7129 : : * Retry. The lock might obviously already be re-acquired by the time
7130 : : * we're attempting to get it again.
7131 : : */
7132 : : }
7133 : :
7134 : 2558930 : return old_buf_state | BM_LOCKED;
7135 : 1279465 : }
7136 : :
7137 : : /*
7138 : : * Wait until the BM_LOCKED flag isn't set anymore and return the buffer's
7139 : : * state at that point.
7140 : : *
7141 : : * Obviously the buffer could be locked by the time the value is returned, so
7142 : : * this is primarily useful in CAS style loops.
7143 : : */
7144 : : pg_noinline uint64
7145 : 195 : WaitBufHdrUnlocked(BufferDesc *buf)
7146 : : {
7147 : 195 : SpinDelayStatus delayStatus;
7148 : 195 : uint64 buf_state;
7149 : :
7150 : 195 : init_local_spin_delay(&delayStatus);
7151 : :
7152 : 195 : buf_state = pg_atomic_read_u64(&buf->state);
7153 : :
7154 [ + + ]: 1322 : while (buf_state & BM_LOCKED)
7155 : : {
7156 : 1127 : perform_spin_delay(&delayStatus);
7157 : 1127 : buf_state = pg_atomic_read_u64(&buf->state);
7158 : : }
7159 : :
7160 : 195 : finish_spin_delay(&delayStatus);
7161 : :
7162 : 390 : return buf_state;
7163 : 195 : }
7164 : :
7165 : : /*
7166 : : * BufferTag comparator.
7167 : : */
7168 : : static inline int
7169 : 0 : buffertag_comparator(const BufferTag *ba, const BufferTag *bb)
7170 : : {
7171 : 0 : int ret;
7172 : 0 : RelFileLocator rlocatora;
7173 : 0 : RelFileLocator rlocatorb;
7174 : :
7175 : 0 : rlocatora = BufTagGetRelFileLocator(ba);
7176 : 0 : rlocatorb = BufTagGetRelFileLocator(bb);
7177 : :
7178 : 0 : ret = rlocator_comparator(&rlocatora, &rlocatorb);
7179 : :
7180 [ # # ]: 0 : if (ret != 0)
7181 : 0 : return ret;
7182 : :
7183 [ # # ]: 0 : if (BufTagGetForkNum(ba) < BufTagGetForkNum(bb))
7184 : 0 : return -1;
7185 [ # # ]: 0 : if (BufTagGetForkNum(ba) > BufTagGetForkNum(bb))
7186 : 0 : return 1;
7187 : :
7188 [ # # ]: 0 : if (ba->blockNum < bb->blockNum)
7189 : 0 : return -1;
7190 [ # # ]: 0 : if (ba->blockNum > bb->blockNum)
7191 : 0 : return 1;
7192 : :
7193 : 0 : return 0;
7194 : 0 : }
7195 : :
7196 : : /*
7197 : : * Comparator determining the writeout order in a checkpoint.
7198 : : *
7199 : : * It is important that tablespaces are compared first, the logic balancing
7200 : : * writes between tablespaces relies on it.
7201 : : */
7202 : : static inline int
7203 : 64239 : ckpt_buforder_comparator(const CkptSortItem *a, const CkptSortItem *b)
7204 : : {
7205 : : /* compare tablespace */
7206 [ + + ]: 64239 : if (a->tsId < b->tsId)
7207 : 61 : return -1;
7208 [ + + ]: 64178 : else if (a->tsId > b->tsId)
7209 : 221 : return 1;
7210 : : /* compare relation */
7211 [ + + ]: 63957 : if (a->relNumber < b->relNumber)
7212 : 12490 : return -1;
7213 [ + + ]: 51467 : else if (a->relNumber > b->relNumber)
7214 : 12338 : return 1;
7215 : : /* compare fork */
7216 [ + + ]: 39129 : else if (a->forkNum < b->forkNum)
7217 : 583 : return -1;
7218 [ + + ]: 38546 : else if (a->forkNum > b->forkNum)
7219 : 712 : return 1;
7220 : : /* compare block number */
7221 [ + + ]: 37834 : else if (a->blockNum < b->blockNum)
7222 : 19491 : return -1;
7223 [ + - ]: 18343 : else if (a->blockNum > b->blockNum)
7224 : 18343 : return 1;
7225 : : /* equal page IDs are unlikely, but not impossible */
7226 : 0 : return 0;
7227 : 64239 : }
7228 : :
7229 : : /*
7230 : : * Comparator for a Min-Heap over the per-tablespace checkpoint completion
7231 : : * progress.
7232 : : */
7233 : : static int
7234 : 4450 : ts_ckpt_progress_comparator(Datum a, Datum b, void *arg)
7235 : : {
7236 : 4450 : CkptTsStatus *sa = (CkptTsStatus *) DatumGetPointer(a);
7237 : 4450 : CkptTsStatus *sb = (CkptTsStatus *) DatumGetPointer(b);
7238 : :
7239 : : /* we want a min-heap, so return 1 for the a < b */
7240 [ + + ]: 4450 : if (sa->progress < sb->progress)
7241 : 4356 : return 1;
7242 [ + + ]: 94 : else if (sa->progress == sb->progress)
7243 : 5 : return 0;
7244 : : else
7245 : 89 : return -1;
7246 : 4450 : }
7247 : :
7248 : : /*
7249 : : * Initialize a writeback context, discarding potential previous state.
7250 : : *
7251 : : * *max_pending is a pointer instead of an immediate value, so the coalesce
7252 : : * limits can easily changed by the GUC mechanism, and so calling code does
7253 : : * not have to check the current configuration. A value of 0 means that no
7254 : : * writeback control will be performed.
7255 : : */
7256 : : void
7257 : 12 : WritebackContextInit(WritebackContext *context, int *max_pending)
7258 : : {
7259 [ + - ]: 12 : Assert(*max_pending <= WRITEBACK_MAX_PENDING_FLUSHES);
7260 : :
7261 : 12 : context->max_pending = max_pending;
7262 : 12 : context->nr_pending = 0;
7263 : 12 : }
7264 : :
7265 : : /*
7266 : : * Add buffer to list of pending writeback requests.
7267 : : */
7268 : : void
7269 : 5230 : ScheduleBufferTagForWriteback(WritebackContext *wb_context, IOContext io_context,
7270 : : BufferTag *tag)
7271 : : {
7272 : 5230 : PendingWriteback *pending;
7273 : :
7274 : : /*
7275 : : * As pg_flush_data() doesn't do anything with fsync disabled, there's no
7276 : : * point in tracking in that case.
7277 : : */
7278 [ + - + - ]: 5230 : if (io_direct_flags & IO_DIRECT_DATA ||
7279 : 5230 : !enableFsync)
7280 : 5230 : return;
7281 : :
7282 : : /*
7283 : : * Add buffer to the pending writeback array, unless writeback control is
7284 : : * disabled.
7285 : : */
7286 [ # # ]: 0 : if (*wb_context->max_pending > 0)
7287 : : {
7288 [ # # ]: 0 : Assert(*wb_context->max_pending <= WRITEBACK_MAX_PENDING_FLUSHES);
7289 : :
7290 : 0 : pending = &wb_context->pending_writebacks[wb_context->nr_pending++];
7291 : :
7292 : 0 : pending->tag = *tag;
7293 : 0 : }
7294 : :
7295 : : /*
7296 : : * Perform pending flushes if the writeback limit is exceeded. This
7297 : : * includes the case where previously an item has been added, but control
7298 : : * is now disabled.
7299 : : */
7300 [ # # ]: 0 : if (wb_context->nr_pending >= *wb_context->max_pending)
7301 : 0 : IssuePendingWritebacks(wb_context, io_context);
7302 [ - + ]: 5230 : }
7303 : :
7304 : : #define ST_SORT sort_pending_writebacks
7305 : : #define ST_ELEMENT_TYPE PendingWriteback
7306 : : #define ST_COMPARE(a, b) buffertag_comparator(&a->tag, &b->tag)
7307 : : #define ST_SCOPE static
7308 : : #define ST_DEFINE
7309 : : #include "lib/sort_template.h"
7310 : :
7311 : : /*
7312 : : * Issue all pending writeback requests, previously scheduled with
7313 : : * ScheduleBufferTagForWriteback, to the OS.
7314 : : *
7315 : : * Because this is only used to improve the OSs IO scheduling we try to never
7316 : : * error out - it's just a hint.
7317 : : */
7318 : : void
7319 : 5 : IssuePendingWritebacks(WritebackContext *wb_context, IOContext io_context)
7320 : : {
7321 : 5 : instr_time io_start;
7322 : 5 : int i;
7323 : :
7324 [ - + ]: 5 : if (wb_context->nr_pending == 0)
7325 : 5 : return;
7326 : :
7327 : : /*
7328 : : * Executing the writes in-order can make them a lot faster, and allows to
7329 : : * merge writeback requests to consecutive blocks into larger writebacks.
7330 : : */
7331 : 0 : sort_pending_writebacks(wb_context->pending_writebacks,
7332 : 0 : wb_context->nr_pending);
7333 : :
7334 : 0 : io_start = pgstat_prepare_io_time(track_io_timing);
7335 : :
7336 : : /*
7337 : : * Coalesce neighbouring writes, but nothing else. For that we iterate
7338 : : * through the, now sorted, array of pending flushes, and look forward to
7339 : : * find all neighbouring (or identical) writes.
7340 : : */
7341 [ # # ]: 0 : for (i = 0; i < wb_context->nr_pending; i++)
7342 : : {
7343 : 0 : PendingWriteback *cur;
7344 : 0 : PendingWriteback *next;
7345 : 0 : SMgrRelation reln;
7346 : 0 : int ahead;
7347 : 0 : BufferTag tag;
7348 : 0 : RelFileLocator currlocator;
7349 : 0 : Size nblocks = 1;
7350 : :
7351 : 0 : cur = &wb_context->pending_writebacks[i];
7352 : 0 : tag = cur->tag;
7353 : 0 : currlocator = BufTagGetRelFileLocator(&tag);
7354 : :
7355 : : /*
7356 : : * Peek ahead, into following writeback requests, to see if they can
7357 : : * be combined with the current one.
7358 : : */
7359 [ # # ]: 0 : for (ahead = 0; i + ahead + 1 < wb_context->nr_pending; ahead++)
7360 : : {
7361 : :
7362 : 0 : next = &wb_context->pending_writebacks[i + ahead + 1];
7363 : :
7364 : : /* different file, stop */
7365 [ # # # # : 0 : if (!RelFileLocatorEquals(currlocator,
# # ]
7366 [ # # ]: 0 : BufTagGetRelFileLocator(&next->tag)) ||
7367 : 0 : BufTagGetForkNum(&cur->tag) != BufTagGetForkNum(&next->tag))
7368 : 0 : break;
7369 : :
7370 : : /* ok, block queued twice, skip */
7371 [ # # ]: 0 : if (cur->tag.blockNum == next->tag.blockNum)
7372 : 0 : continue;
7373 : :
7374 : : /* only merge consecutive writes */
7375 [ # # ]: 0 : if (cur->tag.blockNum + 1 != next->tag.blockNum)
7376 : 0 : break;
7377 : :
7378 : 0 : nblocks++;
7379 : 0 : cur = next;
7380 : 0 : }
7381 : :
7382 : 0 : i += ahead;
7383 : :
7384 : : /* and finally tell the kernel to write the data to storage */
7385 : 0 : reln = smgropen(currlocator, INVALID_PROC_NUMBER);
7386 : 0 : smgrwriteback(reln, BufTagGetForkNum(&tag), tag.blockNum, nblocks);
7387 : 0 : }
7388 : :
7389 : : /*
7390 : : * Assume that writeback requests are only issued for buffers containing
7391 : : * blocks of permanent relations.
7392 : : */
7393 : 0 : pgstat_count_io_op_time(IOOBJECT_RELATION, io_context,
7394 : 0 : IOOP_WRITEBACK, io_start, wb_context->nr_pending, 0);
7395 : :
7396 : 0 : wb_context->nr_pending = 0;
7397 [ - + ]: 5 : }
7398 : :
7399 : : /* ResourceOwner callbacks */
7400 : :
7401 : : static void
7402 : 0 : ResOwnerReleaseBufferIO(Datum res)
7403 : : {
7404 : 0 : Buffer buffer = DatumGetInt32(res);
7405 : :
7406 : 0 : AbortBufferIO(buffer);
7407 : 0 : }
7408 : :
7409 : : static char *
7410 : 0 : ResOwnerPrintBufferIO(Datum res)
7411 : : {
7412 : 0 : Buffer buffer = DatumGetInt32(res);
7413 : :
7414 : 0 : return psprintf("lost track of buffer IO on buffer %d", buffer);
7415 : 0 : }
7416 : :
7417 : : /*
7418 : : * Release buffer as part of resource owner cleanup. This will only be called
7419 : : * if the buffer is pinned. If this backend held the content lock at the time
7420 : : * of the error we also need to release that (note that it is not possible to
7421 : : * hold a content lock without a pin).
7422 : : */
7423 : : static void
7424 : 2211 : ResOwnerReleaseBuffer(Datum res)
7425 : : {
7426 : 2211 : Buffer buffer = DatumGetInt32(res);
7427 : :
7428 : : /* Like ReleaseBuffer, but don't call ResourceOwnerForgetBuffer */
7429 [ + - ]: 2211 : if (!BufferIsValid(buffer))
7430 [ # # # # ]: 0 : elog(ERROR, "bad buffer ID: %d", buffer);
7431 : :
7432 [ + + ]: 2211 : if (BufferIsLocal(buffer))
7433 : 1006 : UnpinLocalBufferNoOwner(buffer);
7434 : : else
7435 : : {
7436 : 1205 : PrivateRefCountEntry *ref;
7437 : :
7438 : 1205 : ref = GetPrivateRefCountEntry(buffer, false);
7439 : :
7440 : : /* not having a private refcount would imply resowner corruption */
7441 [ + - ]: 1205 : Assert(ref != NULL);
7442 : :
7443 : : /*
7444 : : * If the buffer was locked at the time of the resowner release,
7445 : : * release the lock now. This should only happen after errors.
7446 : : */
7447 [ + + ]: 1205 : if (ref->data.lockmode != BUFFER_LOCK_UNLOCK)
7448 : : {
7449 : 4 : BufferDesc *buf = GetBufferDescriptor(buffer - 1);
7450 : :
7451 : 4 : HOLD_INTERRUPTS(); /* match the upcoming RESUME_INTERRUPTS */
7452 : 4 : BufferLockUnlock(buffer, buf);
7453 : 4 : }
7454 : :
7455 : 1205 : UnpinBufferNoOwner(GetBufferDescriptor(buffer - 1));
7456 : 1205 : }
7457 : 2211 : }
7458 : :
7459 : : static char *
7460 : 0 : ResOwnerPrintBuffer(Datum res)
7461 : : {
7462 : 0 : return DebugPrintBufferRefcount(DatumGetInt32(res));
7463 : : }
7464 : :
7465 : : /*
7466 : : * Helper function to evict unpinned buffer whose buffer header lock is
7467 : : * already acquired.
7468 : : */
7469 : : static bool
7470 : 0 : EvictUnpinnedBufferInternal(BufferDesc *desc, bool *buffer_flushed)
7471 : : {
7472 : 0 : uint64 buf_state;
7473 : 0 : bool result;
7474 : :
7475 : 0 : *buffer_flushed = false;
7476 : :
7477 : 0 : buf_state = pg_atomic_read_u64(&(desc->state));
7478 [ # # ]: 0 : Assert(buf_state & BM_LOCKED);
7479 : :
7480 [ # # ]: 0 : if ((buf_state & BM_VALID) == 0)
7481 : : {
7482 : 0 : UnlockBufHdr(desc);
7483 : 0 : return false;
7484 : : }
7485 : :
7486 : : /* Check that it's not pinned already. */
7487 [ # # ]: 0 : if (BUF_STATE_GET_REFCOUNT(buf_state) > 0)
7488 : : {
7489 : 0 : UnlockBufHdr(desc);
7490 : 0 : return false;
7491 : : }
7492 : :
7493 : 0 : PinBuffer_Locked(desc); /* releases spinlock */
7494 : :
7495 : : /* If it was dirty, try to clean it once. */
7496 [ # # ]: 0 : if (buf_state & BM_DIRTY)
7497 : : {
7498 : 0 : FlushUnlockedBuffer(desc, NULL, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
7499 : 0 : *buffer_flushed = true;
7500 : 0 : }
7501 : :
7502 : : /* This will return false if it becomes dirty or someone else pins it. */
7503 : 0 : result = InvalidateVictimBuffer(desc);
7504 : :
7505 : 0 : UnpinBuffer(desc);
7506 : :
7507 : 0 : return result;
7508 : 0 : }
7509 : :
7510 : : /*
7511 : : * Try to evict the current block in a shared buffer.
7512 : : *
7513 : : * This function is intended for testing/development use only!
7514 : : *
7515 : : * To succeed, the buffer must not be pinned on entry, so if the caller had a
7516 : : * particular block in mind, it might already have been replaced by some other
7517 : : * block by the time this function runs. It's also unpinned on return, so the
7518 : : * buffer might be occupied again by the time control is returned, potentially
7519 : : * even by the same block. This inherent raciness without other interlocking
7520 : : * makes the function unsuitable for non-testing usage.
7521 : : *
7522 : : * *buffer_flushed is set to true if the buffer was dirty and has been
7523 : : * flushed, false otherwise. However, *buffer_flushed=true does not
7524 : : * necessarily mean that we flushed the buffer, it could have been flushed by
7525 : : * someone else.
7526 : : *
7527 : : * Returns true if the buffer was valid and it has now been made invalid.
7528 : : * Returns false if it wasn't valid, if it couldn't be evicted due to a pin,
7529 : : * or if the buffer becomes dirty again while we're trying to write it out.
7530 : : */
7531 : : bool
7532 : 0 : EvictUnpinnedBuffer(Buffer buf, bool *buffer_flushed)
7533 : : {
7534 : 0 : BufferDesc *desc;
7535 : :
7536 [ # # ]: 0 : Assert(BufferIsValid(buf) && !BufferIsLocal(buf));
7537 : :
7538 : : /* Make sure we can pin the buffer. */
7539 : 0 : ResourceOwnerEnlarge(CurrentResourceOwner);
7540 : 0 : ReservePrivateRefCountEntry();
7541 : :
7542 : 0 : desc = GetBufferDescriptor(buf - 1);
7543 : 0 : LockBufHdr(desc);
7544 : :
7545 : 0 : return EvictUnpinnedBufferInternal(desc, buffer_flushed);
7546 : 0 : }
7547 : :
7548 : : /*
7549 : : * Try to evict all the shared buffers.
7550 : : *
7551 : : * This function is intended for testing/development use only! See
7552 : : * EvictUnpinnedBuffer().
7553 : : *
7554 : : * The buffers_* parameters are mandatory and indicate the total count of
7555 : : * buffers that:
7556 : : * - buffers_evicted - were evicted
7557 : : * - buffers_flushed - were flushed
7558 : : * - buffers_skipped - could not be evicted
7559 : : */
7560 : : void
7561 : 0 : EvictAllUnpinnedBuffers(int32 *buffers_evicted, int32 *buffers_flushed,
7562 : : int32 *buffers_skipped)
7563 : : {
7564 : 0 : *buffers_evicted = 0;
7565 : 0 : *buffers_skipped = 0;
7566 : 0 : *buffers_flushed = 0;
7567 : :
7568 [ # # ]: 0 : for (int buf = 1; buf <= NBuffers; buf++)
7569 : : {
7570 : 0 : BufferDesc *desc = GetBufferDescriptor(buf - 1);
7571 : 0 : uint64 buf_state;
7572 : 0 : bool buffer_flushed;
7573 : :
7574 [ # # ]: 0 : CHECK_FOR_INTERRUPTS();
7575 : :
7576 : 0 : buf_state = pg_atomic_read_u64(&desc->state);
7577 [ # # ]: 0 : if (!(buf_state & BM_VALID))
7578 : 0 : continue;
7579 : :
7580 : 0 : ResourceOwnerEnlarge(CurrentResourceOwner);
7581 : 0 : ReservePrivateRefCountEntry();
7582 : :
7583 : 0 : LockBufHdr(desc);
7584 : :
7585 [ # # ]: 0 : if (EvictUnpinnedBufferInternal(desc, &buffer_flushed))
7586 : 0 : (*buffers_evicted)++;
7587 : : else
7588 : 0 : (*buffers_skipped)++;
7589 : :
7590 [ # # ]: 0 : if (buffer_flushed)
7591 : 0 : (*buffers_flushed)++;
7592 [ # # # ]: 0 : }
7593 : 0 : }
7594 : :
7595 : : /*
7596 : : * Try to evict all the shared buffers containing provided relation's pages.
7597 : : *
7598 : : * This function is intended for testing/development use only! See
7599 : : * EvictUnpinnedBuffer().
7600 : : *
7601 : : * The caller must hold at least AccessShareLock on the relation to prevent
7602 : : * the relation from being dropped.
7603 : : *
7604 : : * The buffers_* parameters are mandatory and indicate the total count of
7605 : : * buffers that:
7606 : : * - buffers_evicted - were evicted
7607 : : * - buffers_flushed - were flushed
7608 : : * - buffers_skipped - could not be evicted
7609 : : */
7610 : : void
7611 : 0 : EvictRelUnpinnedBuffers(Relation rel, int32 *buffers_evicted,
7612 : : int32 *buffers_flushed, int32 *buffers_skipped)
7613 : : {
7614 [ # # ]: 0 : Assert(!RelationUsesLocalBuffers(rel));
7615 : :
7616 : 0 : *buffers_skipped = 0;
7617 : 0 : *buffers_evicted = 0;
7618 : 0 : *buffers_flushed = 0;
7619 : :
7620 [ # # ]: 0 : for (int buf = 1; buf <= NBuffers; buf++)
7621 : : {
7622 : 0 : BufferDesc *desc = GetBufferDescriptor(buf - 1);
7623 : 0 : uint64 buf_state = pg_atomic_read_u64(&(desc->state));
7624 : 0 : bool buffer_flushed;
7625 : :
7626 [ # # ]: 0 : CHECK_FOR_INTERRUPTS();
7627 : :
7628 : : /* An unlocked precheck should be safe and saves some cycles. */
7629 [ # # # # ]: 0 : if ((buf_state & BM_VALID) == 0 ||
7630 : 0 : !BufTagMatchesRelFileLocator(&desc->tag, &rel->rd_locator))
7631 : 0 : continue;
7632 : :
7633 : : /* Make sure we can pin the buffer. */
7634 : 0 : ResourceOwnerEnlarge(CurrentResourceOwner);
7635 : 0 : ReservePrivateRefCountEntry();
7636 : :
7637 : 0 : buf_state = LockBufHdr(desc);
7638 : :
7639 : : /* recheck, could have changed without the lock */
7640 [ # # # # ]: 0 : if ((buf_state & BM_VALID) == 0 ||
7641 : 0 : !BufTagMatchesRelFileLocator(&desc->tag, &rel->rd_locator))
7642 : : {
7643 : 0 : UnlockBufHdr(desc);
7644 : 0 : continue;
7645 : : }
7646 : :
7647 [ # # ]: 0 : if (EvictUnpinnedBufferInternal(desc, &buffer_flushed))
7648 : 0 : (*buffers_evicted)++;
7649 : : else
7650 : 0 : (*buffers_skipped)++;
7651 : :
7652 [ # # ]: 0 : if (buffer_flushed)
7653 : 0 : (*buffers_flushed)++;
7654 [ # # # ]: 0 : }
7655 : 0 : }
7656 : :
7657 : : /*
7658 : : * Helper function to mark unpinned buffer dirty whose buffer header lock is
7659 : : * already acquired.
7660 : : */
7661 : : static bool
7662 : 0 : MarkDirtyUnpinnedBufferInternal(Buffer buf, BufferDesc *desc,
7663 : : bool *buffer_already_dirty)
7664 : : {
7665 : 0 : uint64 buf_state;
7666 : 0 : bool result = false;
7667 : :
7668 : 0 : *buffer_already_dirty = false;
7669 : :
7670 : 0 : buf_state = pg_atomic_read_u64(&(desc->state));
7671 [ # # ]: 0 : Assert(buf_state & BM_LOCKED);
7672 : :
7673 [ # # ]: 0 : if ((buf_state & BM_VALID) == 0)
7674 : : {
7675 : 0 : UnlockBufHdr(desc);
7676 : 0 : return false;
7677 : : }
7678 : :
7679 : : /* Check that it's not pinned already. */
7680 [ # # ]: 0 : if (BUF_STATE_GET_REFCOUNT(buf_state) > 0)
7681 : : {
7682 : 0 : UnlockBufHdr(desc);
7683 : 0 : return false;
7684 : : }
7685 : :
7686 : : /* Pin the buffer and then release the buffer spinlock */
7687 : 0 : PinBuffer_Locked(desc);
7688 : :
7689 : : /* If it was not already dirty, mark it as dirty. */
7690 [ # # ]: 0 : if (!(buf_state & BM_DIRTY))
7691 : : {
7692 : 0 : BufferLockAcquire(buf, desc, BUFFER_LOCK_EXCLUSIVE);
7693 : 0 : MarkBufferDirty(buf);
7694 : 0 : result = true;
7695 : 0 : BufferLockUnlock(buf, desc);
7696 : 0 : }
7697 : : else
7698 : 0 : *buffer_already_dirty = true;
7699 : :
7700 : 0 : UnpinBuffer(desc);
7701 : :
7702 : 0 : return result;
7703 : 0 : }
7704 : :
7705 : : /*
7706 : : * Try to mark the provided shared buffer as dirty.
7707 : : *
7708 : : * This function is intended for testing/development use only!
7709 : : *
7710 : : * Same as EvictUnpinnedBuffer() but with MarkBufferDirty() call inside.
7711 : : *
7712 : : * The buffer_already_dirty parameter is mandatory and indicate if the buffer
7713 : : * could not be dirtied because it is already dirty.
7714 : : *
7715 : : * Returns true if the buffer has successfully been marked as dirty.
7716 : : */
7717 : : bool
7718 : 0 : MarkDirtyUnpinnedBuffer(Buffer buf, bool *buffer_already_dirty)
7719 : : {
7720 : 0 : BufferDesc *desc;
7721 : 0 : bool buffer_dirtied = false;
7722 : :
7723 [ # # ]: 0 : Assert(!BufferIsLocal(buf));
7724 : :
7725 : : /* Make sure we can pin the buffer. */
7726 : 0 : ResourceOwnerEnlarge(CurrentResourceOwner);
7727 : 0 : ReservePrivateRefCountEntry();
7728 : :
7729 : 0 : desc = GetBufferDescriptor(buf - 1);
7730 : 0 : LockBufHdr(desc);
7731 : :
7732 : 0 : buffer_dirtied = MarkDirtyUnpinnedBufferInternal(buf, desc, buffer_already_dirty);
7733 : : /* Both can not be true at the same time */
7734 [ # # # # ]: 0 : Assert(!(buffer_dirtied && *buffer_already_dirty));
7735 : :
7736 : 0 : return buffer_dirtied;
7737 : 0 : }
7738 : :
7739 : : /*
7740 : : * Try to mark all the shared buffers containing provided relation's pages as
7741 : : * dirty.
7742 : : *
7743 : : * This function is intended for testing/development use only! See
7744 : : * MarkDirtyUnpinnedBuffer().
7745 : : *
7746 : : * The buffers_* parameters are mandatory and indicate the total count of
7747 : : * buffers that:
7748 : : * - buffers_dirtied - were dirtied
7749 : : * - buffers_already_dirty - were already dirty
7750 : : * - buffers_skipped - could not be dirtied because of a reason different
7751 : : * than a buffer being already dirty.
7752 : : */
7753 : : void
7754 : 0 : MarkDirtyRelUnpinnedBuffers(Relation rel,
7755 : : int32 *buffers_dirtied,
7756 : : int32 *buffers_already_dirty,
7757 : : int32 *buffers_skipped)
7758 : : {
7759 [ # # ]: 0 : Assert(!RelationUsesLocalBuffers(rel));
7760 : :
7761 : 0 : *buffers_dirtied = 0;
7762 : 0 : *buffers_already_dirty = 0;
7763 : 0 : *buffers_skipped = 0;
7764 : :
7765 [ # # ]: 0 : for (int buf = 1; buf <= NBuffers; buf++)
7766 : : {
7767 : 0 : BufferDesc *desc = GetBufferDescriptor(buf - 1);
7768 : 0 : uint64 buf_state = pg_atomic_read_u64(&(desc->state));
7769 : 0 : bool buffer_already_dirty;
7770 : :
7771 [ # # ]: 0 : CHECK_FOR_INTERRUPTS();
7772 : :
7773 : : /* An unlocked precheck should be safe and saves some cycles. */
7774 [ # # # # ]: 0 : if ((buf_state & BM_VALID) == 0 ||
7775 : 0 : !BufTagMatchesRelFileLocator(&desc->tag, &rel->rd_locator))
7776 : 0 : continue;
7777 : :
7778 : : /* Make sure we can pin the buffer. */
7779 : 0 : ResourceOwnerEnlarge(CurrentResourceOwner);
7780 : 0 : ReservePrivateRefCountEntry();
7781 : :
7782 : 0 : buf_state = LockBufHdr(desc);
7783 : :
7784 : : /* recheck, could have changed without the lock */
7785 [ # # # # ]: 0 : if ((buf_state & BM_VALID) == 0 ||
7786 : 0 : !BufTagMatchesRelFileLocator(&desc->tag, &rel->rd_locator))
7787 : : {
7788 : 0 : UnlockBufHdr(desc);
7789 : 0 : continue;
7790 : : }
7791 : :
7792 [ # # ]: 0 : if (MarkDirtyUnpinnedBufferInternal(buf, desc, &buffer_already_dirty))
7793 : 0 : (*buffers_dirtied)++;
7794 [ # # ]: 0 : else if (buffer_already_dirty)
7795 : 0 : (*buffers_already_dirty)++;
7796 : : else
7797 : 0 : (*buffers_skipped)++;
7798 [ # # # ]: 0 : }
7799 : 0 : }
7800 : :
7801 : : /*
7802 : : * Try to mark all the shared buffers as dirty.
7803 : : *
7804 : : * This function is intended for testing/development use only! See
7805 : : * MarkDirtyUnpinnedBuffer().
7806 : : *
7807 : : * See MarkDirtyRelUnpinnedBuffers() above for details about the buffers_*
7808 : : * parameters.
7809 : : */
7810 : : void
7811 : 0 : MarkDirtyAllUnpinnedBuffers(int32 *buffers_dirtied,
7812 : : int32 *buffers_already_dirty,
7813 : : int32 *buffers_skipped)
7814 : : {
7815 : 0 : *buffers_dirtied = 0;
7816 : 0 : *buffers_already_dirty = 0;
7817 : 0 : *buffers_skipped = 0;
7818 : :
7819 [ # # ]: 0 : for (int buf = 1; buf <= NBuffers; buf++)
7820 : : {
7821 : 0 : BufferDesc *desc = GetBufferDescriptor(buf - 1);
7822 : 0 : uint64 buf_state;
7823 : 0 : bool buffer_already_dirty;
7824 : :
7825 [ # # ]: 0 : CHECK_FOR_INTERRUPTS();
7826 : :
7827 : 0 : buf_state = pg_atomic_read_u64(&desc->state);
7828 [ # # ]: 0 : if (!(buf_state & BM_VALID))
7829 : 0 : continue;
7830 : :
7831 : 0 : ResourceOwnerEnlarge(CurrentResourceOwner);
7832 : 0 : ReservePrivateRefCountEntry();
7833 : :
7834 : 0 : LockBufHdr(desc);
7835 : :
7836 [ # # ]: 0 : if (MarkDirtyUnpinnedBufferInternal(buf, desc, &buffer_already_dirty))
7837 : 0 : (*buffers_dirtied)++;
7838 [ # # ]: 0 : else if (buffer_already_dirty)
7839 : 0 : (*buffers_already_dirty)++;
7840 : : else
7841 : 0 : (*buffers_skipped)++;
7842 [ # # # ]: 0 : }
7843 : 0 : }
7844 : :
7845 : : /*
7846 : : * Generic implementation of the AIO handle staging callback for readv/writev
7847 : : * on local/shared buffers.
7848 : : *
7849 : : * Each readv/writev can target multiple buffers. The buffers have already
7850 : : * been registered with the IO handle.
7851 : : *
7852 : : * To make the IO ready for execution ("staging"), we need to ensure that the
7853 : : * targeted buffers are in an appropriate state while the IO is ongoing. For
7854 : : * that the AIO subsystem needs to have its own buffer pin, otherwise an error
7855 : : * in this backend could lead to this backend's buffer pin being released as
7856 : : * part of error handling, which in turn could lead to the buffer being
7857 : : * replaced while IO is ongoing.
7858 : : */
7859 : : static pg_attribute_always_inline void
7860 : 7052 : buffer_stage_common(PgAioHandle *ioh, bool is_write, bool is_temp)
7861 : : {
7862 : 7052 : uint64 *io_data;
7863 : 7052 : uint8 handle_data_len;
7864 : 7052 : PgAioWaitRef io_ref;
7865 : 7052 : BufferTag first PG_USED_FOR_ASSERTS_ONLY = {0};
7866 : :
7867 : 7052 : io_data = pgaio_io_get_handle_data(ioh, &handle_data_len);
7868 : :
7869 : 7052 : pgaio_io_get_wref(ioh, &io_ref);
7870 : :
7871 : : /* iterate over all buffers affected by the vectored readv/writev */
7872 [ + + ]: 18202 : for (int i = 0; i < handle_data_len; i++)
7873 : : {
7874 : 11150 : Buffer buffer = (Buffer) io_data[i];
7875 [ + + ]: 11150 : BufferDesc *buf_hdr = is_temp ?
7876 : 2769 : GetLocalBufferDescriptor(-buffer - 1)
7877 : 8381 : : GetBufferDescriptor(buffer - 1);
7878 : 11150 : uint64 buf_state;
7879 : :
7880 : : /*
7881 : : * Check that all the buffers are actually ones that could conceivably
7882 : : * be done in one IO, i.e. are sequential. This is the last
7883 : : * buffer-aware code before IO is actually executed and confusion
7884 : : * about which buffers are targeted by IO can be hard to debug, making
7885 : : * it worth doing extra-paranoid checks.
7886 : : */
7887 [ + + ]: 11150 : if (i == 0)
7888 : 7052 : first = buf_hdr->tag;
7889 : : else
7890 : : {
7891 [ + - ]: 4098 : Assert(buf_hdr->tag.relNumber == first.relNumber);
7892 [ + - ]: 4098 : Assert(buf_hdr->tag.blockNum == first.blockNum + i);
7893 : : }
7894 : :
7895 [ + + ]: 11150 : if (is_temp)
7896 : 2769 : buf_state = pg_atomic_read_u64(&buf_hdr->state);
7897 : : else
7898 : 8381 : buf_state = LockBufHdr(buf_hdr);
7899 : :
7900 : : /* verify the buffer is in the expected state */
7901 [ - + ]: 11150 : Assert(buf_state & BM_TAG_VALID);
7902 [ - + ]: 11150 : if (is_write)
7903 : : {
7904 [ # # ]: 0 : Assert(buf_state & BM_VALID);
7905 [ # # ]: 0 : Assert(buf_state & BM_DIRTY);
7906 : 0 : }
7907 : : else
7908 : : {
7909 [ - + ]: 11150 : Assert(!(buf_state & BM_VALID));
7910 [ - + ]: 11150 : Assert(!(buf_state & BM_DIRTY));
7911 : : }
7912 : :
7913 : : /* temp buffers don't use BM_IO_IN_PROGRESS */
7914 [ + + ]: 11150 : if (!is_temp)
7915 [ - + ]: 8381 : Assert(buf_state & BM_IO_IN_PROGRESS);
7916 : :
7917 [ - + ]: 11150 : Assert(BUF_STATE_GET_REFCOUNT(buf_state) >= 1);
7918 : :
7919 : : /*
7920 : : * Reflect that the buffer is now owned by the AIO subsystem.
7921 : : *
7922 : : * For local buffers: This can't be done just via LocalRefCount, as
7923 : : * one might initially think, as this backend could error out while
7924 : : * AIO is still in progress, releasing all the pins by the backend
7925 : : * itself.
7926 : : *
7927 : : * This pin is released again in TerminateBufferIO().
7928 : : */
7929 : 11150 : buf_hdr->io_wref = io_ref;
7930 : :
7931 [ + + ]: 11150 : if (is_temp)
7932 : : {
7933 : 2769 : buf_state += BUF_REFCOUNT_ONE;
7934 : 2769 : pg_atomic_unlocked_write_u64(&buf_hdr->state, buf_state);
7935 : 2769 : }
7936 : : else
7937 : 8381 : UnlockBufHdrExt(buf_hdr, buf_state, 0, 0, 1);
7938 : :
7939 : : /*
7940 : : * Ensure the content lock that prevents buffer modifications while
7941 : : * the buffer is being written out is not released early due to an
7942 : : * error.
7943 : : */
7944 [ - + # # ]: 11150 : if (is_write && !is_temp)
7945 : : {
7946 [ # # ]: 0 : Assert(BufferLockHeldByMe(buf_hdr));
7947 : :
7948 : : /*
7949 : : * Lock is now owned by AIO subsystem.
7950 : : */
7951 : 0 : BufferLockDisown(buffer, buf_hdr);
7952 : 0 : }
7953 : :
7954 : : /*
7955 : : * Stop tracking this buffer via the resowner - the AIO system now
7956 : : * keeps track.
7957 : : */
7958 [ + + ]: 11150 : if (!is_temp)
7959 : 8381 : ResourceOwnerForgetBufferIO(CurrentResourceOwner, buffer);
7960 : 11150 : }
7961 : 7052 : }
7962 : :
7963 : : /*
7964 : : * Decode readv errors as encoded by buffer_readv_encode_error().
7965 : : */
7966 : : static inline void
7967 : 0 : buffer_readv_decode_error(PgAioResult result,
7968 : : bool *zeroed_any,
7969 : : bool *ignored_any,
7970 : : uint8 *zeroed_or_error_count,
7971 : : uint8 *checkfail_count,
7972 : : uint8 *first_off)
7973 : : {
7974 : 0 : uint32 rem_error = result.error_data;
7975 : :
7976 : : /* see static asserts in buffer_readv_encode_error */
7977 : : #define READV_COUNT_BITS 7
7978 : : #define READV_COUNT_MASK ((1 << READV_COUNT_BITS) - 1)
7979 : :
7980 : 0 : *zeroed_any = rem_error & 1;
7981 : 0 : rem_error >>= 1;
7982 : :
7983 : 0 : *ignored_any = rem_error & 1;
7984 : 0 : rem_error >>= 1;
7985 : :
7986 : 0 : *zeroed_or_error_count = rem_error & READV_COUNT_MASK;
7987 : 0 : rem_error >>= READV_COUNT_BITS;
7988 : :
7989 : 0 : *checkfail_count = rem_error & READV_COUNT_MASK;
7990 : 0 : rem_error >>= READV_COUNT_BITS;
7991 : :
7992 : 0 : *first_off = rem_error & READV_COUNT_MASK;
7993 : 0 : rem_error >>= READV_COUNT_BITS;
7994 : 0 : }
7995 : :
7996 : : /*
7997 : : * Helper to encode errors for buffer_readv_complete()
7998 : : *
7999 : : * Errors are encoded as follows:
8000 : : * - bit 0 indicates whether any page was zeroed (1) or not (0)
8001 : : * - bit 1 indicates whether any checksum failure was ignored (1) or not (0)
8002 : : * - next READV_COUNT_BITS bits indicate the number of errored or zeroed pages
8003 : : * - next READV_COUNT_BITS bits indicate the number of checksum failures
8004 : : * - next READV_COUNT_BITS bits indicate the first offset of the first page
8005 : : * that was errored or zeroed or, if no errors/zeroes, the first ignored
8006 : : * checksum
8007 : : */
8008 : : static inline void
8009 : 0 : buffer_readv_encode_error(PgAioResult *result,
8010 : : bool is_temp,
8011 : : bool zeroed_any,
8012 : : bool ignored_any,
8013 : : uint8 error_count,
8014 : : uint8 zeroed_count,
8015 : : uint8 checkfail_count,
8016 : : uint8 first_error_off,
8017 : : uint8 first_zeroed_off,
8018 : : uint8 first_ignored_off)
8019 : : {
8020 : :
8021 : 0 : uint8 shift = 0;
8022 : 0 : uint8 zeroed_or_error_count =
8023 [ # # ]: 0 : error_count > 0 ? error_count : zeroed_count;
8024 : 0 : uint8 first_off;
8025 : :
8026 : : StaticAssertDecl(PG_IOV_MAX <= 1 << READV_COUNT_BITS,
8027 : : "PG_IOV_MAX is bigger than reserved space for error data");
8028 : : StaticAssertDecl((1 + 1 + 3 * READV_COUNT_BITS) <= PGAIO_RESULT_ERROR_BITS,
8029 : : "PGAIO_RESULT_ERROR_BITS is insufficient for buffer_readv");
8030 : :
8031 : : /*
8032 : : * We only have space to encode one offset - but luckily that's good
8033 : : * enough. If there is an error, the error is the interesting offset, same
8034 : : * with a zeroed buffer vs an ignored buffer.
8035 : : */
8036 [ # # ]: 0 : if (error_count > 0)
8037 : 0 : first_off = first_error_off;
8038 [ # # ]: 0 : else if (zeroed_count > 0)
8039 : 0 : first_off = first_zeroed_off;
8040 : : else
8041 : 0 : first_off = first_ignored_off;
8042 : :
8043 [ # # # # ]: 0 : Assert(!zeroed_any || error_count == 0);
8044 : :
8045 : 0 : result->error_data = 0;
8046 : :
8047 : 0 : result->error_data |= zeroed_any << shift;
8048 : 0 : shift += 1;
8049 : :
8050 : 0 : result->error_data |= ignored_any << shift;
8051 : 0 : shift += 1;
8052 : :
8053 : 0 : result->error_data |= ((uint32) zeroed_or_error_count) << shift;
8054 : 0 : shift += READV_COUNT_BITS;
8055 : :
8056 : 0 : result->error_data |= ((uint32) checkfail_count) << shift;
8057 : 0 : shift += READV_COUNT_BITS;
8058 : :
8059 : 0 : result->error_data |= ((uint32) first_off) << shift;
8060 : 0 : shift += READV_COUNT_BITS;
8061 : :
8062 : 0 : result->id = is_temp ? PGAIO_HCB_LOCAL_BUFFER_READV :
8063 : : PGAIO_HCB_SHARED_BUFFER_READV;
8064 : :
8065 [ # # ]: 0 : if (error_count > 0)
8066 : 0 : result->status = PGAIO_RS_ERROR;
8067 : : else
8068 : 0 : result->status = PGAIO_RS_WARNING;
8069 : :
8070 : : /*
8071 : : * The encoding is complicated enough to warrant cross-checking it against
8072 : : * the decode function.
8073 : : */
8074 : : #ifdef USE_ASSERT_CHECKING
8075 : : {
8076 : 0 : bool zeroed_any_2,
8077 : : ignored_any_2;
8078 : 0 : uint8 zeroed_or_error_count_2,
8079 : : checkfail_count_2,
8080 : : first_off_2;
8081 : :
8082 : 0 : buffer_readv_decode_error(*result,
8083 : : &zeroed_any_2, &ignored_any_2,
8084 : : &zeroed_or_error_count_2,
8085 : : &checkfail_count_2,
8086 : : &first_off_2);
8087 [ # # ]: 0 : Assert(zeroed_any == zeroed_any_2);
8088 [ # # ]: 0 : Assert(ignored_any == ignored_any_2);
8089 [ # # ]: 0 : Assert(zeroed_or_error_count == zeroed_or_error_count_2);
8090 [ # # ]: 0 : Assert(checkfail_count == checkfail_count_2);
8091 [ # # ]: 0 : Assert(first_off == first_off_2);
8092 : 0 : }
8093 : : #endif
8094 : :
8095 : : #undef READV_COUNT_BITS
8096 : : #undef READV_COUNT_MASK
8097 : 0 : }
8098 : :
8099 : : /*
8100 : : * Helper for AIO readv completion callbacks, supporting both shared and temp
8101 : : * buffers. Gets called once for each buffer in a multi-page read.
8102 : : */
8103 : : static pg_attribute_always_inline void
8104 : 9673 : buffer_readv_complete_one(PgAioTargetData *td, uint8 buf_off, Buffer buffer,
8105 : : uint8 flags, bool failed, bool is_temp,
8106 : : bool *buffer_invalid,
8107 : : bool *failed_checksum,
8108 : : bool *ignored_checksum,
8109 : : bool *zeroed_buffer)
8110 : : {
8111 [ + + ]: 9673 : BufferDesc *buf_hdr = is_temp ?
8112 : 2769 : GetLocalBufferDescriptor(-buffer - 1)
8113 : 6904 : : GetBufferDescriptor(buffer - 1);
8114 : 9673 : BufferTag tag = buf_hdr->tag;
8115 : 9673 : char *bufdata = BufferGetBlock(buffer);
8116 : 9673 : uint64 set_flag_bits;
8117 : 9673 : int piv_flags;
8118 : :
8119 : : /* check that the buffer is in the expected state for a read */
8120 : : #ifdef USE_ASSERT_CHECKING
8121 : : {
8122 : 9673 : uint64 buf_state = pg_atomic_read_u64(&buf_hdr->state);
8123 : :
8124 [ + - ]: 9673 : Assert(buf_state & BM_TAG_VALID);
8125 [ + - ]: 9673 : Assert(!(buf_state & BM_VALID));
8126 : : /* temp buffers don't use BM_IO_IN_PROGRESS */
8127 [ + + ]: 9673 : if (!is_temp)
8128 [ + - ]: 6904 : Assert(buf_state & BM_IO_IN_PROGRESS);
8129 [ + - ]: 9673 : Assert(!(buf_state & BM_DIRTY));
8130 : 9673 : }
8131 : : #endif
8132 : :
8133 : 9673 : *buffer_invalid = false;
8134 : 9673 : *failed_checksum = false;
8135 : 9673 : *ignored_checksum = false;
8136 : 9673 : *zeroed_buffer = false;
8137 : :
8138 : : /*
8139 : : * We ask PageIsVerified() to only log the message about checksum errors,
8140 : : * as the completion might be run in any backend (or IO workers). We will
8141 : : * report checksum errors in buffer_readv_report().
8142 : : */
8143 : 9673 : piv_flags = PIV_LOG_LOG;
8144 : :
8145 : : /* the local zero_damaged_pages may differ from the definer's */
8146 [ + - ]: 9673 : if (flags & READ_BUFFERS_IGNORE_CHECKSUM_FAILURES)
8147 : 0 : piv_flags |= PIV_IGNORE_CHECKSUM_FAILURE;
8148 : :
8149 : : /* Check for garbage data. */
8150 [ - + ]: 9673 : if (!failed)
8151 : : {
8152 : : /*
8153 : : * If the buffer is not currently pinned by this backend, e.g. because
8154 : : * we're completing this IO after an error, the buffer data will have
8155 : : * been marked as inaccessible when the buffer was unpinned. The AIO
8156 : : * subsystem holds a pin, but that doesn't prevent the buffer from
8157 : : * having been marked as inaccessible. The completion might also be
8158 : : * executed in a different process.
8159 : : */
8160 : : #ifdef USE_VALGRIND
8161 : : if (!BufferIsPinned(buffer))
8162 : : VALGRIND_MAKE_MEM_DEFINED(bufdata, BLCKSZ);
8163 : : #endif
8164 : :
8165 [ + - + - ]: 19346 : if (!PageIsVerified((Page) bufdata, tag.blockNum, piv_flags,
8166 : 9673 : failed_checksum))
8167 : : {
8168 [ # # ]: 0 : if (flags & READ_BUFFERS_ZERO_ON_ERROR)
8169 : : {
8170 : 0 : memset(bufdata, 0, BLCKSZ);
8171 : 0 : *zeroed_buffer = true;
8172 : 0 : }
8173 : : else
8174 : : {
8175 : 0 : *buffer_invalid = true;
8176 : : /* mark buffer as having failed */
8177 : 0 : failed = true;
8178 : : }
8179 : 0 : }
8180 [ + - ]: 9673 : else if (*failed_checksum)
8181 : 0 : *ignored_checksum = true;
8182 : :
8183 : : /* undo what we did above */
8184 : : #ifdef USE_VALGRIND
8185 : : if (!BufferIsPinned(buffer))
8186 : : VALGRIND_MAKE_MEM_NOACCESS(bufdata, BLCKSZ);
8187 : : #endif
8188 : :
8189 : : /*
8190 : : * Immediately log a message about the invalid page, but only to the
8191 : : * server log. The reason to do so immediately is that this may be
8192 : : * executed in a different backend than the one that originated the
8193 : : * request. The reason to do so immediately is that the originator
8194 : : * might not process the query result immediately (because it is busy
8195 : : * doing another part of query processing) or at all (e.g. if it was
8196 : : * cancelled or errored out due to another IO also failing). The
8197 : : * definer of the IO will emit an ERROR or WARNING when processing the
8198 : : * IO's results
8199 : : *
8200 : : * To avoid duplicating the code to emit these log messages, we reuse
8201 : : * buffer_readv_report().
8202 : : */
8203 [ + - + - : 9673 : if (*buffer_invalid || *failed_checksum || *zeroed_buffer)
- + ]
8204 : : {
8205 : 0 : PgAioResult result_one = {0};
8206 : :
8207 : 0 : buffer_readv_encode_error(&result_one, is_temp,
8208 : 0 : *zeroed_buffer,
8209 : 0 : *ignored_checksum,
8210 : 0 : *buffer_invalid,
8211 : 0 : *zeroed_buffer ? 1 : 0,
8212 : 0 : *failed_checksum ? 1 : 0,
8213 : 0 : buf_off, buf_off, buf_off);
8214 : 0 : pgaio_result_report(result_one, td, LOG_SERVER_ONLY);
8215 : 0 : }
8216 : 9673 : }
8217 : :
8218 : : /* Terminate I/O and set BM_VALID. */
8219 : 9673 : set_flag_bits = failed ? BM_IO_ERROR : BM_VALID;
8220 [ + + ]: 9673 : if (is_temp)
8221 : 2769 : TerminateLocalBufferIO(buf_hdr, false, set_flag_bits, true);
8222 : : else
8223 : 6904 : TerminateBufferIO(buf_hdr, false, set_flag_bits, false, true);
8224 : :
8225 : : /*
8226 : : * Call the BUFFER_READ_DONE tracepoint in the callback, even though the
8227 : : * callback may not be executed in the same backend that called
8228 : : * BUFFER_READ_START. The alternative would be to defer calling the
8229 : : * tracepoint to a later point (e.g. the local completion callback for
8230 : : * shared buffer reads), which seems even less helpful.
8231 : : */
8232 : 9673 : TRACE_POSTGRESQL_BUFFER_READ_DONE(tag.forkNum,
8233 : : tag.blockNum,
8234 : : tag.spcOid,
8235 : : tag.dbOid,
8236 : : tag.relNumber,
8237 : : is_temp ? MyProcNumber : INVALID_PROC_NUMBER,
8238 : : false);
8239 : 9673 : }
8240 : :
8241 : : /*
8242 : : * Perform completion handling of a single AIO read. This read may cover
8243 : : * multiple blocks / buffers.
8244 : : *
8245 : : * Shared between shared and local buffers, to reduce code duplication.
8246 : : */
8247 : : static pg_attribute_always_inline PgAioResult
8248 : 6681 : buffer_readv_complete(PgAioHandle *ioh, PgAioResult prior_result,
8249 : : uint8 cb_data, bool is_temp)
8250 : : {
8251 : 6681 : PgAioResult result = prior_result;
8252 : 6681 : PgAioTargetData *td = pgaio_io_get_target_data(ioh);
8253 : 6681 : uint8 first_error_off = 0;
8254 : 6681 : uint8 first_zeroed_off = 0;
8255 : 6681 : uint8 first_ignored_off = 0;
8256 : 6681 : uint8 error_count = 0;
8257 : 6681 : uint8 zeroed_count = 0;
8258 : 6681 : uint8 ignored_count = 0;
8259 : 6681 : uint8 checkfail_count = 0;
8260 : 6681 : uint64 *io_data;
8261 : 6681 : uint8 handle_data_len;
8262 : :
8263 [ + + ]: 6681 : if (is_temp)
8264 : : {
8265 [ + - ]: 582 : Assert(td->smgr.is_temp);
8266 [ + - ]: 582 : Assert(pgaio_io_get_owner(ioh) == MyProcNumber);
8267 : 582 : }
8268 : : else
8269 [ + - ]: 6099 : Assert(!td->smgr.is_temp);
8270 : :
8271 : : /*
8272 : : * Iterate over all the buffers affected by this IO and call the
8273 : : * per-buffer completion function for each buffer.
8274 : : */
8275 : 6681 : io_data = pgaio_io_get_handle_data(ioh, &handle_data_len);
8276 [ + + ]: 16354 : for (uint8 buf_off = 0; buf_off < handle_data_len; buf_off++)
8277 : : {
8278 : 9673 : Buffer buf = io_data[buf_off];
8279 : 9673 : bool failed;
8280 : 9673 : bool failed_verification = false;
8281 : 9673 : bool failed_checksum = false;
8282 : 9673 : bool zeroed_buffer = false;
8283 : 9673 : bool ignored_checksum = false;
8284 : :
8285 [ + - ]: 9673 : Assert(BufferIsValid(buf));
8286 : :
8287 : : /*
8288 : : * If the entire I/O failed on a lower-level, each buffer needs to be
8289 : : * marked as failed. In case of a partial read, the first few buffers
8290 : : * may be ok.
8291 : : */
8292 : 9673 : failed =
8293 : 9673 : prior_result.status == PGAIO_RS_ERROR
8294 [ - + ]: 9673 : || prior_result.result <= buf_off;
8295 : :
8296 : 9673 : buffer_readv_complete_one(td, buf_off, buf, cb_data, failed, is_temp,
8297 : : &failed_verification,
8298 : : &failed_checksum,
8299 : : &ignored_checksum,
8300 : : &zeroed_buffer);
8301 : :
8302 : : /*
8303 : : * Track information about the number of different kinds of error
8304 : : * conditions across all pages, as there can be multiple pages failing
8305 : : * verification as part of one IO.
8306 : : */
8307 [ - + # # : 9673 : if (failed_verification && !zeroed_buffer && error_count++ == 0)
# # ]
8308 : 0 : first_error_off = buf_off;
8309 [ - + # # ]: 9673 : if (zeroed_buffer && zeroed_count++ == 0)
8310 : 0 : first_zeroed_off = buf_off;
8311 [ - + # # ]: 9673 : if (ignored_checksum && ignored_count++ == 0)
8312 : 0 : first_ignored_off = buf_off;
8313 [ + - ]: 9673 : if (failed_checksum)
8314 : 0 : checkfail_count++;
8315 : 9673 : }
8316 : :
8317 : : /*
8318 : : * If the smgr read succeeded [partially] and page verification failed for
8319 : : * some of the pages, adjust the IO's result state appropriately.
8320 : : */
8321 [ + - - + ]: 13362 : if (prior_result.status != PGAIO_RS_ERROR &&
8322 [ + - + - ]: 6681 : (error_count > 0 || ignored_count > 0 || zeroed_count > 0))
8323 : : {
8324 : 0 : buffer_readv_encode_error(&result, is_temp,
8325 : 0 : zeroed_count > 0, ignored_count > 0,
8326 : 0 : error_count, zeroed_count, checkfail_count,
8327 : 0 : first_error_off, first_zeroed_off,
8328 : 0 : first_ignored_off);
8329 : 0 : pgaio_result_report(result, td, DEBUG1);
8330 : 0 : }
8331 : :
8332 : : /*
8333 : : * For shared relations this reporting is done in
8334 : : * shared_buffer_readv_complete_local().
8335 : : */
8336 [ + + + - ]: 6681 : if (is_temp && checkfail_count > 0)
8337 : 0 : pgstat_report_checksum_failures_in_db(td->smgr.rlocator.dbOid,
8338 : 0 : checkfail_count);
8339 : :
8340 : : return result;
8341 : 6681 : }
8342 : :
8343 : : /*
8344 : : * AIO error reporting callback for aio_shared_buffer_readv_cb and
8345 : : * aio_local_buffer_readv_cb.
8346 : : *
8347 : : * The error is encoded / decoded in buffer_readv_encode_error() /
8348 : : * buffer_readv_decode_error().
8349 : : */
8350 : : static void
8351 : 0 : buffer_readv_report(PgAioResult result, const PgAioTargetData *td,
8352 : : int elevel)
8353 : : {
8354 : 0 : int nblocks = td->smgr.nblocks;
8355 : 0 : BlockNumber first = td->smgr.blockNum;
8356 : 0 : BlockNumber last = first + nblocks - 1;
8357 : 0 : ProcNumber errProc =
8358 [ # # ]: 0 : td->smgr.is_temp ? MyProcNumber : INVALID_PROC_NUMBER;
8359 : 0 : RelPathStr rpath =
8360 : 0 : relpathbackend(td->smgr.rlocator, errProc, td->smgr.forkNum);
8361 : 0 : bool zeroed_any,
8362 : : ignored_any;
8363 : 0 : uint8 zeroed_or_error_count,
8364 : : checkfail_count,
8365 : : first_off;
8366 : 0 : uint8 affected_count;
8367 : 0 : const char *msg_one,
8368 : : *msg_mult,
8369 : : *det_mult,
8370 : : *hint_mult;
8371 : :
8372 : 0 : buffer_readv_decode_error(result, &zeroed_any, &ignored_any,
8373 : : &zeroed_or_error_count,
8374 : : &checkfail_count,
8375 : : &first_off);
8376 : :
8377 : : /*
8378 : : * Treat a read that had both zeroed buffers *and* ignored checksums as a
8379 : : * special case, it's too irregular to be emitted the same way as the
8380 : : * other cases.
8381 : : */
8382 [ # # # # ]: 0 : if (zeroed_any && ignored_any)
8383 : : {
8384 [ # # ]: 0 : Assert(zeroed_any && ignored_any);
8385 [ # # ]: 0 : Assert(nblocks > 1); /* same block can't be both zeroed and ignored */
8386 [ # # ]: 0 : Assert(result.status != PGAIO_RS_ERROR);
8387 : 0 : affected_count = zeroed_or_error_count;
8388 : :
8389 [ # # # # : 0 : ereport(elevel,
# # # # #
# # # ]
8390 : : errcode(ERRCODE_DATA_CORRUPTED),
8391 : : errmsg("zeroing %u page(s) and ignoring %u checksum failure(s) among blocks %u..%u of relation \"%s\"",
8392 : : affected_count, checkfail_count, first, last, rpath.str),
8393 : : affected_count > 1 ?
8394 : : errdetail("Block %u held the first zeroed page.",
8395 : : first + first_off) : 0,
8396 : : errhint_plural("See server log for details about the other %d invalid block.",
8397 : : "See server log for details about the other %d invalid blocks.",
8398 : : affected_count + checkfail_count - 1,
8399 : : affected_count + checkfail_count - 1));
8400 : 0 : return;
8401 : : }
8402 : :
8403 : : /*
8404 : : * The other messages are highly repetitive. To avoid duplicating a long
8405 : : * and complicated ereport(), gather the translated format strings
8406 : : * separately and then do one common ereport.
8407 : : */
8408 [ # # ]: 0 : if (result.status == PGAIO_RS_ERROR)
8409 : : {
8410 [ # # ]: 0 : Assert(!zeroed_any); /* can't have invalid pages when zeroing them */
8411 : 0 : affected_count = zeroed_or_error_count;
8412 : 0 : msg_one = _("invalid page in block %u of relation \"%s\"");
8413 : 0 : msg_mult = _("%u invalid pages among blocks %u..%u of relation \"%s\"");
8414 : 0 : det_mult = _("Block %u held the first invalid page.");
8415 : 0 : hint_mult = _("See server log for the other %u invalid block(s).");
8416 : 0 : }
8417 [ # # # # ]: 0 : else if (zeroed_any && !ignored_any)
8418 : : {
8419 : 0 : affected_count = zeroed_or_error_count;
8420 : 0 : msg_one = _("invalid page in block %u of relation \"%s\"; zeroing out page");
8421 : 0 : msg_mult = _("zeroing out %u invalid pages among blocks %u..%u of relation \"%s\"");
8422 : 0 : det_mult = _("Block %u held the first zeroed page.");
8423 : 0 : hint_mult = _("See server log for the other %u zeroed block(s).");
8424 : 0 : }
8425 [ # # ]: 0 : else if (!zeroed_any && ignored_any)
8426 : : {
8427 : 0 : affected_count = checkfail_count;
8428 : 0 : msg_one = _("ignoring checksum failure in block %u of relation \"%s\"");
8429 : 0 : msg_mult = _("ignoring %u checksum failures among blocks %u..%u of relation \"%s\"");
8430 : 0 : det_mult = _("Block %u held the first ignored page.");
8431 : 0 : hint_mult = _("See server log for the other %u ignored block(s).");
8432 : 0 : }
8433 : : else
8434 : 0 : pg_unreachable();
8435 : :
8436 [ # # # # : 0 : ereport(elevel,
# # # # #
# # # # #
# # ]
8437 : : errcode(ERRCODE_DATA_CORRUPTED),
8438 : : affected_count == 1 ?
8439 : : errmsg_internal(msg_one, first + first_off, rpath.str) :
8440 : : errmsg_internal(msg_mult, affected_count, first, last, rpath.str),
8441 : : affected_count > 1 ? errdetail_internal(det_mult, first + first_off) : 0,
8442 : : affected_count > 1 ? errhint_internal(hint_mult, affected_count - 1) : 0);
8443 [ # # ]: 0 : }
8444 : :
8445 : : static void
8446 : 6470 : shared_buffer_readv_stage(PgAioHandle *ioh, uint8 cb_data)
8447 : : {
8448 : 6470 : buffer_stage_common(ioh, false, false);
8449 : 6470 : }
8450 : :
8451 : : static PgAioResult
8452 : 6099 : shared_buffer_readv_complete(PgAioHandle *ioh, PgAioResult prior_result,
8453 : : uint8 cb_data)
8454 : : {
8455 : 6099 : return buffer_readv_complete(ioh, prior_result, cb_data, false);
8456 : : }
8457 : :
8458 : : /*
8459 : : * We need a backend-local completion callback for shared buffers, to be able
8460 : : * to report checksum errors correctly. Unfortunately that can only safely
8461 : : * happen if the reporting backend has previously called
8462 : : * pgstat_prepare_report_checksum_failure(), which we can only guarantee in
8463 : : * the backend that started the IO. Hence this callback.
8464 : : */
8465 : : static PgAioResult
8466 : 6470 : shared_buffer_readv_complete_local(PgAioHandle *ioh, PgAioResult prior_result,
8467 : : uint8 cb_data)
8468 : : {
8469 : 6470 : bool zeroed_any,
8470 : : ignored_any;
8471 : 6470 : uint8 zeroed_or_error_count,
8472 : : checkfail_count,
8473 : : first_off;
8474 : :
8475 [ + - ]: 6470 : if (prior_result.status == PGAIO_RS_OK)
8476 : 6470 : return prior_result;
8477 : :
8478 : 0 : buffer_readv_decode_error(prior_result,
8479 : : &zeroed_any,
8480 : : &ignored_any,
8481 : : &zeroed_or_error_count,
8482 : : &checkfail_count,
8483 : : &first_off);
8484 : :
8485 [ # # ]: 0 : if (checkfail_count)
8486 : : {
8487 : 0 : PgAioTargetData *td = pgaio_io_get_target_data(ioh);
8488 : :
8489 : 0 : pgstat_report_checksum_failures_in_db(td->smgr.rlocator.dbOid,
8490 : 0 : checkfail_count);
8491 : 0 : }
8492 : :
8493 : 0 : return prior_result;
8494 : 6470 : }
8495 : :
8496 : : static void
8497 : 582 : local_buffer_readv_stage(PgAioHandle *ioh, uint8 cb_data)
8498 : : {
8499 : 582 : buffer_stage_common(ioh, false, true);
8500 : 582 : }
8501 : :
8502 : : static PgAioResult
8503 : 582 : local_buffer_readv_complete(PgAioHandle *ioh, PgAioResult prior_result,
8504 : : uint8 cb_data)
8505 : : {
8506 : 582 : return buffer_readv_complete(ioh, prior_result, cb_data, true);
8507 : : }
8508 : :
8509 : : /* readv callback is passed READ_BUFFERS_* flags as callback data */
8510 : : const PgAioHandleCallbacks aio_shared_buffer_readv_cb = {
8511 : : .stage = shared_buffer_readv_stage,
8512 : : .complete_shared = shared_buffer_readv_complete,
8513 : : /* need a local callback to report checksum failures */
8514 : : .complete_local = shared_buffer_readv_complete_local,
8515 : : .report = buffer_readv_report,
8516 : : };
8517 : :
8518 : : /* readv callback is passed READ_BUFFERS_* flags as callback data */
8519 : : const PgAioHandleCallbacks aio_local_buffer_readv_cb = {
8520 : : .stage = local_buffer_readv_stage,
8521 : :
8522 : : /*
8523 : : * Note that this, in contrast to the shared_buffers case, uses
8524 : : * complete_local, as only the issuing backend has access to the required
8525 : : * datastructures. This is important in case the IO completion may be
8526 : : * consumed incidentally by another backend.
8527 : : */
8528 : : .complete_local = local_buffer_readv_complete,
8529 : : .report = buffer_readv_report,
8530 : : };
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