10000 Add routine able to update the control file to src/common/ · postgrespro/postgres_cluster@ce6afc6 · GitHub
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michaelpqmichaelpq
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Add routine able to update the control file to src/common/
This adds a new routine to src/common/ which is compatible with both the frontend and backend code, able to update the control file's contents. This is now getting used only by pg_rewind, but some upcoming patches which add more control on checksums for offline instances will make use of it. This could also get used more by the backend as xlog.c has its own flavor of the same logic with some wait events and an additional flush phase before closing the opened file descriptor, but this is let as separate work. Author: Michael Banck, Michael Paquier Reviewed-by: Fabien Coelho, Sergei Kornilov Discussion: https://postgr.es/m/20181221201616.GD4974@nighthawk.caipicrew.dd-dns.de
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3 files changed

+101
-42
lines changed

3 files changed

+101
-42
lines changed

‎src/bin/pg_rewind/pg_rewind.c

Lines changed: 2 additions & 41 deletions
Original file line numberDiff line numberDiff line change
@@ -24,6 +24,7 @@
2424
#include "access/xlog_internal.h"
2525
#include "catalog/catversion.h"
2626
#include "catalog/pg_control.h"
27+
#include "common/controldata_utils.h"
2728
#include "common/file_perm.h"
2829
#include "common/file_utils.h"
2930
#include "common/restricted_token.h"
@@ -37,7 +38,6 @@ static void createBackupLabel(XLogRecPtr startpoint, TimeLineID starttli,
3738

3839
static void digestControlFile(ControlFileData *ControlFile, char *source,
3940
size_t size);
40-
static void updateControlFile(ControlFileData *ControlFile);
4141
static void syncTargetDirectory(void);
4242
static void sanityChecks(void);
4343
static void findCommonAncestorTimeline(XLogRecPtr *recptr, int *tliIndex);
@@ -377,7 +377,7 @@ main(int argc, char **argv)
377377
ControlFile_new.minRecoveryPoint = endrec;
378378
ControlFile_new.minRecoveryPointTLI = endtli;
379379
ControlFile_new.state = DB_IN_ARCHIVE_RECOVERY;
380-
updateControlFile(&ControlFile_new);
380+
update_controlfile(datadir_target, progname, &ControlFile_new);
381381

382382
pg_log(PG_PROGRESS, "syncing target data directory\n");
383383
syncTargetDirectory();
@@ -666,45 +666,6 @@ digestControlFile(ControlFileData *ControlFile, char *src, size_t size)
666666
checkControlFile(ControlFile);
667667
}
668668

669-
/*
670-
* Update the target's control file.
671-
*/
672-
static void
673-
updateControlFile(ControlFileData *ControlFile)
674-
{
675-
char buffer[PG_CONTROL_FILE_SIZE];
676-
677-
/*
678-
* For good luck, apply the same static assertions as in backend's
679-
* WriteControlFile().
680-
*/
681-
StaticAssertStmt(sizeof(ControlFileData) <= PG_CONTROL_MAX_SAFE_SIZE,
682-
"pg_control is too large for atomic disk writes");
683-
StaticAssertStmt(sizeof(ControlFileData) <= PG_CONTROL_FILE_SIZE,
684-
"sizeof(ControlFileData) exceeds PG_CONTROL_FILE_SIZE");
685-
686-
/* Recalculate CRC of control file */
687-
INIT_CRC32C(ControlFile->crc);
688-
COMP_CRC32C(ControlFile->crc,
689-
(char *) ControlFile,
690-
offsetof(ControlFileData, crc));
691-
FIN_CRC32C(ControlFile->crc);
692-
693-
/*
694-
* Write out PG_CONTROL_FILE_SIZE bytes into pg_control by zero-padding
695-
* the excess over sizeof(ControlFileData), to avoid premature EOF related
696-
* errors when reading it.
697-
*/
698-
memset(buffer, 0, PG_CONTROL_FILE_SIZE);
699-
memcpy(buffer, ControlFile, sizeof(ControlFileData));
700-
701-
open_target_file("global/pg_control", false);
702-
703-
write_target_range(buffer, 0, PG_CONTROL_FILE_SIZE);
704-
705-
close_target_file();
706-
}
707-
708669
/*
709670
* Sync target data directory to ensure that modifications are safely on disk.
710671
*

‎src/common/controldata_utils.c

Lines changed: 94 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -24,8 +24,10 @@
2424
#include <sys/stat.h>
2525
#include <fcntl.h>
2626

27+
#include "access/xlog_internal.h"
2728
#include "catalog/pg_control.h"
2829
#include "common/controldata_utils.h"
30+
#include "common/file_perm.h"
2931
#include "port/pg_crc32c.h"
3032
#ifndef FRONTEND
3133
#include "storage/fd.h"
@@ -137,3 +139,95 @@ get_controlfile(const char *DataDir, const char *progname, bool *crc_ok_p)
137139

138140
return ControlFile;
139141
}
142+
143+
/*
144+
* update_controlfile()
145+
*
146+
* Update controlfile values with the contents given by caller. The
147+
* contents to write are included in "ControlFile". Note that it is up
148+
* to the caller to fsync the updated file, and to properly lock
149+
* ControlFileLock when calling this routine in the backend.
150+
*/
151+
void
152+
update_controlfile(const char *DataDir, const char *progname,
153+
ControlFileData *ControlFile)
154+
{
155+
int fd;
156+
char buffer[PG_CONTROL_FILE_SIZE];
157+
char ControlFilePath[MAXPGPATH];
158+
159+
/*
160+
* Apply the same static assertions as in backend's WriteControlFile().
161+
*/
162+
StaticAssertStmt(sizeof(ControlFileData) <= PG_CONTROL_MAX_SAFE_SIZE,
163+
"pg_control is too large for atomic disk writes");
164+
StaticAssertStmt(sizeof(ControlFileData) <= PG_CONTROL_FILE_SIZE,
165+
"sizeof(ControlFileData) exceeds PG_CONTROL_FILE_SIZE");
166+
167+
/* Recalculate CRC of control file */
168+
INIT_CRC32C(ControlFile->crc);
169+
COMP_CRC32C(ControlFile->crc,
170+
(char *) ControlFile,
171+
offsetof(ControlFileData, crc));
172+
FIN_CRC32C(ControlFile->crc);
173+
174+
/*
175+
* Write out PG_CONTROL_FILE_SIZE bytes into pg_control by zero-padding
176+
* the excess over sizeof(ControlFileData), to avoid premature EOF related
177+
* errors when reading it.
178+
*/
179+
memset(buffer, 0, PG_CONTROL_FILE_SIZE);
180+
memcpy(buffer, ControlFile, sizeof(ControlFileData));
181+
182+
snprintf(ControlFilePath, sizeof(ControlFilePath), "%s/%s", DataDir, XLOG_CONTROL_FILE);
183+
184+
#ifndef FRONTEND
185+
if ((fd = OpenTransientFile(ControlFilePath, O_WRONLY | PG_BINARY)) == -1)
186+
ereport(PANIC,
187+
(errcode_for_file_access(),
188+
errmsg("could not open file \"%s\": %m",
189+
ControlFilePath)));
190+
#else
191+
if ((fd = open(ControlFilePath, O_WRONLY | PG_BINARY,
192+
pg_file_create_mode)) == -1)
193+
{
194+
fprintf(stderr, _("%s: could not open file \"%s\": %s\n"),
195+
progname, ControlFilePath, strerror(errno));
196+
exit(EXIT_FAILURE);
197+
}
198+
#endif
199+
200+
errno = 0;
201+
if (write(fd, buffer, PG_CONTROL_FILE_SIZE) != PG_CONTROL_FILE_SIZE)
202+
{
203+
/* if write didn't set errno, assume problem is no disk space */
204+
if (errno == 0)
205+
errno = ENOSPC;
206+
207+
#ifndef FRONTEND
208+
ereport(PANIC,
209+
(errcode_for_file_access(),
210+
errmsg("could not write file \"%s\": %m",
211+
ControlFilePath)));
212+
#else
213+
fprintf(stderr, _("%s: could not write \"%s\": %s\n"),
214+
progname, ControlFilePath, strerror(errno));
215+
exit(EXIT_FAILURE);
216+
#endif
217+
}
218+
219+
#ifndef FRONTEND
220+
if (CloseTransientFile(fd))
221+
ereport(PANIC,
222+
(errcode_for_file_access(),
223+
errmsg("could not close file \"%s\": %m",
224+
ControlFilePath)));
225+
#else
226+
if (close(fd) < 0)
227+
{
228+
fprintf(stderr, _("%s: could not close file \"%s\": %s\n"),
229+
progname, ControlFilePath, strerror(errno));
230+
exit(EXIT_FAILURE);
231+
}
232+
#endif
233+
}

‎src/include/common/controldata_utils.h

Lines changed: 5 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -12,6 +12,10 @@
1212

1313
#include "catalog/pg_control.h"
1414

15-
extern ControlFileData *get_controlfile(const char *DataDir, const char *progname, bool *crc_ok_p);
15+
extern ControlFileData *get_controlfile(const char *DataDir,
16+
const char *progname,
17+
bool *crc_ok_p);
18+
extern void update_controlfile(const char *DataDir, const char *progname,
19+
ControlFileData *ControlFile);
1620

1721
#endif /* COMMON_CONTROLDATA_UTILS_H */

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