Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * controldata_utils.c
4 : * Common code for control data file output.
5 : *
6 : *
7 : * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
8 : * Portions Copyright (c) 1994, Regents of the University of California
9 : *
10 : *
11 : * IDENTIFICATION
12 : * src/common/controldata_utils.c
13 : *
14 : *-------------------------------------------------------------------------
15 : */
16 :
17 : #ifndef FRONTEND
18 : #include "postgres.h"
19 : #else
20 : #include "postgres_fe.h"
21 : #endif
22 :
23 : #include <unistd.h>
24 : #include <sys/stat.h>
25 : #include <fcntl.h>
26 : #include <time.h>
27 :
28 : #include "access/xlog_internal.h"
29 : #include "catalog/pg_control.h"
30 : #include "common/controldata_utils.h"
31 : #ifdef FRONTEND
32 : #include "common/file_perm.h"
33 : #include "common/logging.h"
34 : #endif
35 : #include "port/pg_crc32c.h"
36 :
37 : #ifndef FRONTEND
38 : #include "pgstat.h"
39 : #include "storage/fd.h"
40 : #endif
41 :
42 : /*
43 : * get_controlfile()
44 : *
45 : * Get controlfile values. The result is returned as a palloc'd copy of the
46 : * control file data.
47 : *
48 : * crc_ok_p can be used by the caller to see whether the CRC of the control
49 : * file data is correct.
50 : */
51 : ControlFileData *
52 590 : get_controlfile(const char *DataDir, bool *crc_ok_p)
53 : {
54 : char ControlFilePath[MAXPGPATH];
55 :
56 590 : snprintf(ControlFilePath, MAXPGPATH, "%s/%s", DataDir, XLOG_CONTROL_FILE);
57 :
58 590 : return get_controlfile_by_exact_path(ControlFilePath, crc_ok_p);
59 : }
60 :
61 : /*
62 : * get_controlfile_by_exact_path()
63 : *
64 : * As above, but the caller specifies the path to the control file itself,
65 : * rather than the path to the data directory.
66 : */
67 : ControlFileData *
68 782 : get_controlfile_by_exact_path(const char *ControlFilePath, bool *crc_ok_p)
69 : {
70 : ControlFileData *ControlFile;
71 : int fd;
72 : pg_crc32c crc;
73 : int r;
74 : #ifdef FRONTEND
75 : pg_crc32c last_crc;
76 726 : int retries = 0;
77 : #endif
78 :
79 : Assert(crc_ok_p);
80 :
81 782 : ControlFile = palloc_object(ControlFileData);
82 :
83 : #ifdef FRONTEND
84 726 : INIT_CRC32C(last_crc);
85 :
86 728 : retry:
87 : #endif
88 :
89 : #ifndef FRONTEND
90 56 : if ((fd = OpenTransientFile(ControlFilePath, O_RDONLY | PG_BINARY)) == -1)
91 0 : ereport(ERROR,
92 : (errcode_for_file_access(),
93 : errmsg("could not open file \"%s\" for reading: %m",
94 : ControlFilePath)));
95 : #else
96 728 : if ((fd = open(ControlFilePath, O_RDONLY | PG_BINARY, 0)) == -1)
97 2 : pg_fatal("could not open file \"%s\" for reading: %m",
98 : ControlFilePath);
99 : #endif
100 :
101 782 : r = read(fd, ControlFile, sizeof(ControlFileData));
102 782 : if (r != sizeof(ControlFileData))
103 : {
104 0 : if (r < 0)
105 : #ifndef FRONTEND
106 0 : ereport(ERROR,
107 : (errcode_for_file_access(),
108 : errmsg("could not read file \"%s\": %m", ControlFilePath)));
109 : #else
110 0 : pg_fatal("could not read file \"%s\": %m", ControlFilePath);
111 : #endif
112 : else
113 : #ifndef FRONTEND
114 0 : ereport(ERROR,
115 : (errcode(ERRCODE_DATA_CORRUPTED),
116 : errmsg("could not read file \"%s\": read %d of %zu",
117 : ControlFilePath, r, sizeof(ControlFileData))));
118 : #else
119 0 : pg_fatal("could not read file \"%s\": read %d of %zu",
120 : ControlFilePath, r, sizeof(ControlFileData));
121 : #endif
122 : }
123 :
124 : #ifndef FRONTEND
125 56 : if (CloseTransientFile(fd) != 0)
126 0 : ereport(ERROR,
127 : (errcode_for_file_access(),
128 : errmsg("could not close file \"%s\": %m",
129 : ControlFilePath)));
130 : #else
131 726 : if (close(fd) != 0)
132 0 : pg_fatal("could not close file \"%s\": %m", ControlFilePath);
133 : #endif
134 :
135 : /* Check the CRC. */
136 782 : INIT_CRC32C(crc);
137 782 : COMP_CRC32C(crc,
138 : ControlFile,
139 : offsetof(ControlFileData, crc));
140 782 : FIN_CRC32C(crc);
141 :
142 782 : *crc_ok_p = EQ_CRC32C(crc, ControlFile->crc);
143 :
144 : #ifdef FRONTEND
145 :
146 : /*
147 : * If the server was writing at the same time, it is possible that we read
148 : * partially updated contents on some systems. If the CRC doesn't match,
149 : * retry a limited number of times until we compute the same bad CRC twice
150 : * in a row with a short sleep in between. Then the failure is unlikely
151 : * to be due to a concurrent write.
152 : */
153 726 : if (!*crc_ok_p &&
154 4 : (retries == 0 || !EQ_CRC32C(crc, last_crc)) &&
155 : retries < 10)
156 : {
157 2 : retries++;
158 2 : last_crc = crc;
159 2 : pg_usleep(10000);
160 2 : goto retry;
161 : }
162 : #endif
163 :
164 : /* Make sure the control file is valid byte order. */
165 780 : if (ControlFile->pg_control_version % 65536 == 0 &&
166 2 : ControlFile->pg_control_version / 65536 != 0)
167 : #ifndef FRONTEND
168 0 : elog(ERROR, _("byte ordering mismatch"));
169 : #else
170 0 : pg_log_warning("possible byte ordering mismatch\n"
171 : "The byte ordering used to store the pg_control file might not match the one\n"
172 : "used by this program. In that case the results below would be incorrect, and\n"
173 : "the PostgreSQL installation would be incompatible with this data directory.");
174 : #endif
175 :
176 780 : return ControlFile;
177 : }
178 :
179 : /*
180 : * update_controlfile()
181 : *
182 : * Update controlfile values with the contents given by caller. The
183 : * contents to write are included in "ControlFile". "do_sync" can be
184 : * optionally used to flush the updated control file. Note that it is up
185 : * to the caller to properly lock ControlFileLock when calling this
186 : * routine in the backend.
187 : */
188 : void
189 17718 : update_controlfile(const char *DataDir,
190 : ControlFileData *ControlFile, bool do_sync)
191 : {
192 : int fd;
193 : char buffer[PG_CONTROL_FILE_SIZE];
194 : char ControlFilePath[MAXPGPATH];
195 :
196 : /* Update timestamp */
197 17718 : ControlFile->time = (pg_time_t) time(NULL);
198 :
199 : /* Recalculate CRC of control file */
200 17718 : INIT_CRC32C(ControlFile->crc);
201 17718 : COMP_CRC32C(ControlFile->crc,
202 : ControlFile,
203 : offsetof(ControlFileData, crc));
204 17718 : FIN_CRC32C(ControlFile->crc);
205 :
206 : /*
207 : * Write out PG_CONTROL_FILE_SIZE bytes into pg_control by zero-padding
208 : * the excess over sizeof(ControlFileData), to avoid premature EOF related
209 : * errors when reading it.
210 : */
211 17718 : memset(buffer, 0, PG_CONTROL_FILE_SIZE);
212 17718 : memcpy(buffer, ControlFile, sizeof(ControlFileData));
213 :
214 17718 : snprintf(ControlFilePath, sizeof(ControlFilePath), "%s/%s", DataDir, XLOG_CONTROL_FILE);
215 :
216 : #ifndef FRONTEND
217 :
218 : /*
219 : * All errors issue a PANIC, so no need to use OpenTransientFile() and to
220 : * worry about file descriptor leaks.
221 : */
222 17558 : if ((fd = BasicOpenFile(ControlFilePath, O_RDWR | PG_BINARY)) < 0)
223 0 : ereport(PANIC,
224 : (errcode_for_file_access(),
225 : errmsg("could not open file \"%s\": %m",
226 : ControlFilePath)));
227 : #else
228 160 : if ((fd = open(ControlFilePath, O_WRONLY | PG_BINARY,
229 : pg_file_create_mode)) == -1)
230 0 : pg_fatal("could not open file \"%s\": %m", ControlFilePath);
231 : #endif
232 :
233 17718 : errno = 0;
234 : #ifndef FRONTEND
235 17558 : pgstat_report_wait_start(WAIT_EVENT_CONTROL_FILE_WRITE_UPDATE);
236 : #endif
237 17718 : if (write(fd, buffer, PG_CONTROL_FILE_SIZE) != PG_CONTROL_FILE_SIZE)
238 : {
239 : /* if write didn't set errno, assume problem is no disk space */
240 0 : if (errno == 0)
241 0 : errno = ENOSPC;
242 :
243 : #ifndef FRONTEND
244 0 : ereport(PANIC,
245 : (errcode_for_file_access(),
246 : errmsg("could not write file \"%s\": %m",
247 : ControlFilePath)));
248 : #else
249 0 : pg_fatal("could not write file \"%s\": %m", ControlFilePath);
250 : #endif
251 : }
252 : #ifndef FRONTEND
253 17558 : pgstat_report_wait_end();
254 : #endif
255 :
256 17718 : if (do_sync)
257 : {
258 : #ifndef FRONTEND
259 17558 : pgstat_report_wait_start(WAIT_EVENT_CONTROL_FILE_SYNC_UPDATE);
260 17558 : if (pg_fsync(fd) != 0)
261 0 : ereport(PANIC,
262 : (errcode_for_file_access(),
263 : errmsg("could not fsync file \"%s\": %m",
264 : ControlFilePath)));
265 17558 : pgstat_report_wait_end();
266 : #else
267 134 : if (fsync(fd) != 0)
268 0 : pg_fatal("could not fsync file \"%s\": %m", ControlFilePath);
269 : #endif
270 : }
271 :
272 17718 : if (close(fd) != 0)
273 : {
274 : #ifndef FRONTEND
275 0 : ereport(PANIC,
276 : (errcode_for_file_access(),
277 : errmsg("could not close file \"%s\": %m",
278 : ControlFilePath)));
279 : #else
280 0 : pg_fatal("could not close file \"%s\": %m", ControlFilePath);
281 : #endif
282 : }
283 17718 : }
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