Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * astreamer_file.c
4 : *
5 : * Archive streamers that write to files. astreamer_plain_writer writes
6 : * the whole archive to a single file, and astreamer_extractor writes
7 : * each archive member to a separate file in a given directory.
8 : *
9 : * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
10 : *
11 : * IDENTIFICATION
12 : * src/fe_utils/astreamer_file.c
13 : *-------------------------------------------------------------------------
14 : */
15 :
16 : #include "postgres_fe.h"
17 :
18 : #include <unistd.h>
19 :
20 : #include "common/file_perm.h"
21 : #include "common/logging.h"
22 : #include "fe_utils/astreamer.h"
23 :
24 : typedef struct astreamer_plain_writer
25 : {
26 : astreamer base;
27 : char *pathname;
28 : FILE *file;
29 : bool should_close_file;
30 : } astreamer_plain_writer;
31 :
32 : typedef struct astreamer_extractor
33 : {
34 : astreamer base;
35 : char *basepath;
36 : const char *(*link_map) (const char *);
37 : void (*report_output_file) (const char *);
38 : char filename[MAXPGPATH];
39 : FILE *file;
40 : } astreamer_extractor;
41 :
42 : static void astreamer_plain_writer_content(astreamer *streamer,
43 : astreamer_member *member,
44 : const char *data, int len,
45 : astreamer_archive_context context);
46 : static void astreamer_plain_writer_finalize(astreamer *streamer);
47 : static void astreamer_plain_writer_free(astreamer *streamer);
48 :
49 : static const astreamer_ops astreamer_plain_writer_ops = {
50 : .content = astreamer_plain_writer_content,
51 : .finalize = astreamer_plain_writer_finalize,
52 : .free = astreamer_plain_writer_free
53 : };
54 :
55 : static void astreamer_extractor_content(astreamer *streamer,
56 : astreamer_member *member,
57 : const char *data, int len,
58 : astreamer_archive_context context);
59 : static void astreamer_extractor_finalize(astreamer *streamer);
60 : static void astreamer_extractor_free(astreamer *streamer);
61 : static void extract_directory(const char *filename, mode_t mode);
62 : static void extract_link(const char *filename, const char *linktarget);
63 : static FILE *create_file_for_extract(const char *filename, mode_t mode);
64 :
65 : static const astreamer_ops astreamer_extractor_ops = {
66 : .content = astreamer_extractor_content,
67 : .finalize = astreamer_extractor_finalize,
68 : .free = astreamer_extractor_free
69 : };
70 :
71 : /*
72 : * Create a astreamer that just writes data to a file.
73 : *
74 : * The caller must specify a pathname and may specify a file. The pathname is
75 : * used for error-reporting purposes either way. If file is NULL, the pathname
76 : * also identifies the file to which the data should be written: it is opened
77 : * for writing and closed when done. If file is not NULL, the data is written
78 : * there.
79 : */
80 : astreamer *
81 0 : astreamer_plain_writer_new(char *pathname, FILE *file)
82 : {
83 0 : astreamer_plain_writer *streamer;
84 :
85 0 : streamer = palloc0_object(astreamer_plain_writer);
86 0 : *((const astreamer_ops **) &streamer->base.bbs_ops) =
87 : &astreamer_plain_writer_ops;
88 :
89 0 : streamer->pathname = pstrdup(pathname);
90 0 : streamer->file = file;
91 :
92 0 : if (file == NULL)
93 : {
94 0 : streamer->file = fopen(pathname, "wb");
95 0 : if (streamer->file == NULL)
96 0 : pg_fatal("could not create file \"%s\": %m", pathname);
97 0 : streamer->should_close_file = true;
98 0 : }
99 :
100 0 : return &streamer->base;
101 0 : }
102 :
103 : /*
104 : * Write archive content to file.
105 : */
106 : static void
107 0 : astreamer_plain_writer_content(astreamer *streamer,
108 : astreamer_member *member, const char *data,
109 : int len, astreamer_archive_context context)
110 : {
111 0 : astreamer_plain_writer *mystreamer;
112 :
113 0 : mystreamer = (astreamer_plain_writer *) streamer;
114 :
115 0 : if (len == 0)
116 0 : return;
117 :
118 0 : errno = 0;
119 0 : if (fwrite(data, len, 1, mystreamer->file) != 1)
120 : {
121 : /* if write didn't set errno, assume problem is no disk space */
122 0 : if (errno == 0)
123 0 : errno = ENOSPC;
124 0 : pg_fatal("could not write to file \"%s\": %m",
125 : mystreamer->pathname);
126 0 : }
127 0 : }
128 :
129 : /*
130 : * End-of-archive processing when writing to a plain file consists of closing
131 : * the file if we opened it, but not if the caller provided it.
132 : */
133 : static void
134 0 : astreamer_plain_writer_finalize(astreamer *streamer)
135 : {
136 0 : astreamer_plain_writer *mystreamer;
137 :
138 0 : mystreamer = (astreamer_plain_writer *) streamer;
139 :
140 0 : if (mystreamer->should_close_file && fclose(mystreamer->file) != 0)
141 0 : pg_fatal("could not close file \"%s\": %m",
142 : mystreamer->pathname);
143 :
144 0 : mystreamer->file = NULL;
145 0 : mystreamer->should_close_file = false;
146 0 : }
147 :
148 : /*
149 : * Free memory associated with this astreamer.
150 : */
151 : static void
152 0 : astreamer_plain_writer_free(astreamer *streamer)
153 : {
154 0 : astreamer_plain_writer *mystreamer;
155 :
156 0 : mystreamer = (astreamer_plain_writer *) streamer;
157 :
158 0 : Assert(!mystreamer->should_close_file);
159 0 : Assert(mystreamer->base.bbs_next == NULL);
160 :
161 0 : pfree(mystreamer->pathname);
162 0 : pfree(mystreamer);
163 0 : }
164 :
165 : /*
166 : * Create a astreamer that extracts an archive.
167 : *
168 : * All pathnames in the archive are interpreted relative to basepath.
169 : *
170 : * Unlike e.g. astreamer_plain_writer_new() we can't do anything useful here
171 : * with untyped chunks; we need typed chunks which follow the rules described
172 : * in astreamer.h. Assuming we have that, we don't need to worry about the
173 : * original archive format; it's enough to just look at the member information
174 : * provided and write to the corresponding file.
175 : *
176 : * 'link_map' is a function that will be applied to the target of any
177 : * symbolic link, and which should return a replacement pathname to be used
178 : * in its place. If NULL, the symbolic link target is used without
179 : * modification.
180 : *
181 : * 'report_output_file' is a function that will be called each time we open a
182 : * new output file. The pathname to that file is passed as an argument. If
183 : * NULL, the call is skipped.
184 : */
185 : astreamer *
186 0 : astreamer_extractor_new(const char *basepath,
187 : const char *(*link_map) (const char *),
188 : void (*report_output_file) (const char *))
189 : {
190 0 : astreamer_extractor *streamer;
191 :
192 0 : streamer = palloc0_object(astreamer_extractor);
193 0 : *((const astreamer_ops **) &streamer->base.bbs_ops) =
194 : &astreamer_extractor_ops;
195 0 : streamer->basepath = pstrdup(basepath);
196 0 : streamer->link_map = link_map;
197 0 : streamer->report_output_file = report_output_file;
198 :
199 0 : return &streamer->base;
200 0 : }
201 :
202 : /*
203 : * Extract archive contents to the filesystem.
204 : */
205 : static void
206 0 : astreamer_extractor_content(astreamer *streamer, astreamer_member *member,
207 : const char *data, int len,
208 : astreamer_archive_context context)
209 : {
210 0 : astreamer_extractor *mystreamer = (astreamer_extractor *) streamer;
211 0 : int fnamelen;
212 :
213 0 : Assert(member != NULL || context == ASTREAMER_ARCHIVE_TRAILER);
214 0 : Assert(context != ASTREAMER_UNKNOWN);
215 :
216 0 : switch (context)
217 : {
218 : case ASTREAMER_MEMBER_HEADER:
219 0 : Assert(mystreamer->file == NULL);
220 :
221 : /* Prepend basepath. */
222 0 : snprintf(mystreamer->filename, sizeof(mystreamer->filename),
223 0 : "%s/%s", mystreamer->basepath, member->pathname);
224 :
225 : /* Remove any trailing slash. */
226 0 : fnamelen = strlen(mystreamer->filename);
227 0 : if (mystreamer->filename[fnamelen - 1] == '/')
228 0 : mystreamer->filename[fnamelen - 1] = '\0';
229 :
230 : /* Dispatch based on file type. */
231 0 : if (member->is_directory)
232 0 : extract_directory(mystreamer->filename, member->mode);
233 0 : else if (member->is_link)
234 : {
235 0 : const char *linktarget = member->linktarget;
236 :
237 0 : if (mystreamer->link_map)
238 0 : linktarget = mystreamer->link_map(linktarget);
239 0 : extract_link(mystreamer->filename, linktarget);
240 0 : }
241 : else
242 0 : mystreamer->file =
243 0 : create_file_for_extract(mystreamer->filename,
244 0 : member->mode);
245 :
246 : /* Report output file change. */
247 0 : if (mystreamer->report_output_file)
248 0 : mystreamer->report_output_file(mystreamer->filename);
249 0 : break;
250 :
251 : case ASTREAMER_MEMBER_CONTENTS:
252 0 : if (mystreamer->file == NULL)
253 0 : break;
254 :
255 0 : errno = 0;
256 0 : if (len > 0 && fwrite(data, len, 1, mystreamer->file) != 1)
257 : {
258 : /* if write didn't set errno, assume problem is no disk space */
259 0 : if (errno == 0)
260 0 : errno = ENOSPC;
261 0 : pg_fatal("could not write to file \"%s\": %m",
262 : mystreamer->filename);
263 0 : }
264 0 : break;
265 :
266 : case ASTREAMER_MEMBER_TRAILER:
267 0 : if (mystreamer->file == NULL)
268 0 : break;
269 0 : fclose(mystreamer->file);
270 0 : mystreamer->file = NULL;
271 0 : break;
272 :
273 : case ASTREAMER_ARCHIVE_TRAILER:
274 : break;
275 :
276 : default:
277 : /* Shouldn't happen. */
278 0 : pg_fatal("unexpected state while extracting archive");
279 0 : }
280 0 : }
281 :
282 : /*
283 : * Should we tolerate an already-existing directory?
284 : *
285 : * When streaming WAL, pg_wal (or pg_xlog for pre-9.6 clusters) will have been
286 : * created by the wal receiver process. Also, when the WAL directory location
287 : * was specified, pg_wal (or pg_xlog) has already been created as a symbolic
288 : * link before starting the actual backup. So just ignore creation failures
289 : * on related directories.
290 : *
291 : * If in-place tablespaces are used, pg_tblspc and subdirectories may already
292 : * exist when we get here. So tolerate that case, too.
293 : */
294 : static bool
295 0 : should_allow_existing_directory(const char *pathname)
296 : {
297 0 : const char *filename = last_dir_separator(pathname) + 1;
298 :
299 0 : if (strcmp(filename, "pg_wal") == 0 ||
300 0 : strcmp(filename, "pg_xlog") == 0 ||
301 0 : strcmp(filename, "archive_status") == 0 ||
302 0 : strcmp(filename, "summaries") == 0 ||
303 0 : strcmp(filename, "pg_tblspc") == 0)
304 0 : return true;
305 :
306 0 : if (strspn(filename, "0123456789") == strlen(filename))
307 : {
308 0 : const char *pg_tblspc = strstr(pathname, "/pg_tblspc/");
309 :
310 0 : return pg_tblspc != NULL && pg_tblspc + 11 == filename;
311 0 : }
312 :
313 0 : return false;
314 0 : }
315 :
316 : /*
317 : * Create a directory.
318 : */
319 : static void
320 0 : extract_directory(const char *filename, mode_t mode)
321 : {
322 0 : if (mkdir(filename, pg_dir_create_mode) != 0 &&
323 0 : (errno != EEXIST || !should_allow_existing_directory(filename)))
324 0 : pg_fatal("could not create directory \"%s\": %m",
325 : filename);
326 :
327 : #ifndef WIN32
328 0 : if (chmod(filename, mode))
329 0 : pg_fatal("could not set permissions on directory \"%s\": %m",
330 : filename);
331 : #endif
332 0 : }
333 :
334 : /*
335 : * Create a symbolic link.
336 : *
337 : * It's most likely a link in pg_tblspc directory, to the location of a
338 : * tablespace. Apply any tablespace mapping given on the command line
339 : * (--tablespace-mapping). (We blindly apply the mapping without checking that
340 : * the link really is inside pg_tblspc. We don't expect there to be other
341 : * symlinks in a data directory, but if there are, you can call it an
342 : * undocumented feature that you can map them too.)
343 : */
344 : static void
345 0 : extract_link(const char *filename, const char *linktarget)
346 : {
347 0 : if (symlink(linktarget, filename) != 0)
348 0 : pg_fatal("could not create symbolic link from \"%s\" to \"%s\": %m",
349 : filename, linktarget);
350 0 : }
351 :
352 : /*
353 : * Create a regular file.
354 : *
355 : * Return the resulting handle so we can write the content to the file.
356 : */
357 : static FILE *
358 0 : create_file_for_extract(const char *filename, mode_t mode)
359 : {
360 0 : FILE *file;
361 :
362 0 : file = fopen(filename, "wb");
363 0 : if (file == NULL)
364 0 : pg_fatal("could not create file \"%s\": %m", filename);
365 :
366 : #ifndef WIN32
367 0 : if (chmod(filename, mode))
368 0 : pg_fatal("could not set permissions on file \"%s\": %m",
369 : filename);
370 : #endif
371 :
372 0 : return file;
373 0 : }
374 :
375 : /*
376 : * End-of-stream processing for extracting an archive.
377 : *
378 : * There's nothing to do here but sanity checking.
379 : */
380 : static void
381 0 : astreamer_extractor_finalize(astreamer *streamer)
382 : {
383 0 : astreamer_extractor *mystreamer PG_USED_FOR_ASSERTS_ONLY
384 0 : = (astreamer_extractor *) streamer;
385 :
386 0 : Assert(mystreamer->file == NULL);
387 0 : }
388 :
389 : /*
390 : * Free memory.
391 : */
392 : static void
393 0 : astreamer_extractor_free(astreamer *streamer)
394 : {
395 0 : astreamer_extractor *mystreamer = (astreamer_extractor *) streamer;
396 :
397 0 : pfree(mystreamer->basepath);
398 0 : pfree(mystreamer);
399 0 : }
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