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Commitbfa282a

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Avoid unlikely data-loss scenarios due to rename() without fsync.
Renaming a file using rename(2) is not guaranteed to be durable in faceof crashes. Use the previously added durable_rename()/durable_link_or_rename()in various places where we previously just renamed files.Most of the changed call sites are arguably not critical, but it seemsbetter to err on the side of too much durability. The most prominentknown case where the previously missing fsyncs could cause data loss iscrashes at the end of a checkpoint. After the actual checkpoint has beenperformed, old WAL files are recycled. When they're filled, theircontents are fdatasynced, but we did not fsync the containingdirectory. An OS/hardware crash in an unfortunate moment could then endup leaving that file with its old name, but new content; WAL replaywould thus not replay it.Reported-By: Tomas VondraAuthor: Michael Paquier, Tomas Vondra, Andres FreundDiscussion: 56583BDD.9060302@2ndquadrant.comBackpatch: All supported branches
1 parente069848 commitbfa282a

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5 files changed

+17
-88
lines changed

5 files changed

+17
-88
lines changed

‎contrib/pg_stat_statements/pg_stat_statements.c

Lines changed: 1 addition & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -588,11 +588,7 @@ pgss_shmem_shutdown(int code, Datum arg)
588588
/*
589589
* Rename file into place, so we atomically replace the old one.
590590
*/
591-
if (rename(PGSS_DUMP_FILE".tmp",PGSS_DUMP_FILE)!=0)
592-
ereport(LOG,
593-
(errcode_for_file_access(),
594-
errmsg("could not rename pg_stat_statement file \"%s\": %m",
595-
PGSS_DUMP_FILE".tmp")));
591+
(void)durable_rename(PGSS_DUMP_FILE".tmp",PGSS_DUMP_FILE,LOG);
596592

597593
return;
598594

‎src/backend/access/transam/timeline.c

Lines changed: 6 additions & 34 deletions
Original file line numberDiff line numberDiff line change
@@ -418,24 +418,10 @@ writeTimeLineHistory(TimeLineID newTLI, TimeLineID parentTLI,
418418
TLHistoryFilePath(path,newTLI);
419419

420420
/*
421-
* Prefer link() to rename() here just to be really sure that we don't
422-
* overwrite an existing file. However, there shouldn't be one, so
423-
* rename() is an acceptable substitute except for the truly paranoid.
421+
* Perform the rename using link if available, paranoidly trying to avoid
422+
* overwriting an existing file (there shouldn't be one).
424423
*/
425-
#ifHAVE_WORKING_LINK
426-
if (link(tmppath,path)<0)
427-
ereport(ERROR,
428-
(errcode_for_file_access(),
429-
errmsg("could not link file \"%s\" to \"%s\": %m",
430-
tmppath,path)));
431-
unlink(tmppath);
432-
#else
433-
if (rename(tmppath,path)<0)
434-
ereport(ERROR,
435-
(errcode_for_file_access(),
436-
errmsg("could not rename file \"%s\" to \"%s\": %m",
437-
tmppath,path)));
438-
#endif
424+
durable_link_or_rename(tmppath,path,ERROR);
439425

440426
/* The history file can be archived immediately. */
441427
if (XLogArchivingActive())
@@ -508,24 +494,10 @@ writeTimeLineHistoryFile(TimeLineID tli, char *content, int size)
508494
TLHistoryFilePath(path,tli);
509495

510496
/*
511-
* Prefer link() to rename() here just to be really sure that we don't
512-
* overwrite an existing logfile. However, there shouldn't be one, so
513-
* rename() is an acceptable substitute except for the truly paranoid.
497+
* Perform the rename using link if available, paranoidly trying to avoid
498+
* overwriting an existing file (there shouldn't be one).
514499
*/
515-
#ifHAVE_WORKING_LINK
516-
if (link(tmppath,path)<0)
517-
ereport(ERROR,
518-
(errcode_for_file_access(),
519-
errmsg("could not link file \"%s\" to \"%s\": %m",
520-
tmppath,path)));
521-
unlink(tmppath);
522-
#else
523-
if (rename(tmppath,path)<0)
524-
ereport(ERROR,
525-
(errcode_for_file_access(),
526-
errmsg("could not rename file \"%s\" to \"%s\": %m",
527-
tmppath,path)));
528-
#endif
500+
durable_link_or_rename(tmppath,path,ERROR);
529501
}
530502

531503
/*

‎src/backend/access/transam/xlog.c

Lines changed: 7 additions & 33 deletions
Original file line numberDiff line numberDiff line change
@@ -2553,34 +2553,16 @@ InstallXLogFileSegment(XLogSegNo *segno, char *tmppath,
25532553
}
25542554

25552555
/*
2556-
* Prefer link() to rename() here just to be really sure that we don't
2557-
* overwrite an existing logfile. However, there shouldn't be one, so
2558-
* rename() is an acceptable substitute except for the truly paranoid.
2556+
* Perform the rename using link if available, paranoidly trying to avoid
2557+
* overwriting an existing file (there shouldn't be one).
25592558
*/
2560-
#ifHAVE_WORKING_LINK
2561-
if (link(tmppath,path)<0)
2559+
if (durable_link_or_rename(tmppath,path,LOG)!=0)
25622560
{
25632561
if (use_lock)
25642562
LWLockRelease(ControlFileLock);
2565-
ereport(LOG,
2566-
(errcode_for_file_access(),
2567-
errmsg("could not link file \"%s\" to \"%s\" (initialization of log file): %m",
2568-
tmppath,path)));
2569-
return false;
2570-
}
2571-
unlink(tmppath);
2572-
#else
2573-
if (rename(tmppath,path)<0)
2574-
{
2575-
if (use_lock)
2576-
LWLockRelease(ControlFileLock);
2577-
ereport(LOG,
2578-
(errcode_for_file_access(),
2579-
errmsg("could not rename file \"%s\" to \"%s\" (initialization of log file): %m",
2580-
tmppath,path)));
2563+
/* durable_link_or_rename already emitted log message */
25812564
return false;
25822565
}
2583-
#endif
25842566

25852567
if (use_lock)
25862568
LWLockRelease(ControlFileLock);
@@ -4474,11 +4456,7 @@ exitArchiveRecovery(TimeLineID endTLI, XLogSegNo endLogSegNo)
44744456
* re-enter archive recovery mode in a subsequent crash.
44754457
*/
44764458
unlink(RECOVERY_COMMAND_DONE);
4477-
if (rename(RECOVERY_COMMAND_FILE,RECOVERY_COMMAND_DONE)!=0)
4478-
ereport(FATAL,
4479-
(errcode_for_file_access(),
4480-
errmsg("could not rename file \"%s\" to \"%s\": %m",
4481-
RECOVERY_COMMAND_FILE,RECOVERY_COMMAND_DONE)));
4459+
durable_rename(RECOVERY_COMMAND_FILE,RECOVERY_COMMAND_DONE,FATAL);
44824460

44834461
ereport(LOG,
44844462
(errmsg("archive recovery complete")));
@@ -5472,11 +5450,7 @@ StartupXLOG(void)
54725450
if (haveBackupLabel)
54735451
{
54745452
unlink(BACKUP_LABEL_OLD);
5475-
if (rename(BACKUP_LABEL_FILE,BACKUP_LABEL_OLD)!=0)
5476-
ereport(FATAL,
5477-
(errcode_for_file_access(),
5478-
errmsg("could not rename file \"%s\" to \"%s\": %m",
5479-
BACKUP_LABEL_FILE,BACKUP_LABEL_OLD)));
5453+
durable_rename(BACKUP_LABEL_FILE,BACKUP_LABEL_OLD,FATAL);
54805454
}
54815455

54825456
/* Check that the GUCs used to generate the WAL allow recovery */
@@ -9524,7 +9498,7 @@ CancelBackup(void)
95249498
/* remove leftover file from previously canceled backup if it exists */
95259499
unlink(BACKUP_LABEL_OLD);
95269500

9527-
if (rename(BACKUP_LABEL_FILE,BACKUP_LABEL_OLD)==0)
9501+
if (durable_rename(BACKUP_LABEL_FILE,BACKUP_LABEL_OLD,DEBUG1)==0)
95289502
{
95299503
ereport(LOG,
95309504
(errmsg("online backup mode canceled"),

‎src/backend/access/transam/xlogarchive.c

Lines changed: 2 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -468,11 +468,7 @@ KeepFileRestoredFromArchive(char *path, char *xlogfname)
468468
reload= true;
469469
}
470470

471-
if (rename(path,xlogfpath)<0)
472-
ereport(ERROR,
473-
(errcode_for_file_access(),
474-
errmsg("could not rename file \"%s\" to \"%s\": %m",
475-
path,xlogfpath)));
471+
durable_rename(path,xlogfpath,ERROR);
476472

477473
/*
478474
* Create .done file forcibly to prevent the restored segment from being
@@ -575,12 +571,7 @@ XLogArchiveForceDone(const char *xlog)
575571
StatusFilePath(archiveReady,xlog,".ready");
576572
if (stat(archiveReady,&stat_buf)==0)
577573
{
578-
if (rename(archiveReady,archiveDone)<0)
579-
ereport(WARNING,
580-
(errcode_for_file_access(),
581-
errmsg("could not rename file \"%s\" to \"%s\": %m",
582-
archiveReady,archiveDone)));
583-
574+
(void)durable_rename(archiveReady,archiveDone,WARNING);
584575
return;
585576
}
586577

‎src/backend/postmaster/pgarch.c

Lines changed: 1 addition & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -750,9 +750,5 @@ pgarch_archiveDone(char *xlog)
750750

751751
StatusFilePath(rlogready,xlog,".ready");
752752
StatusFilePath(rlogdone,xlog,".done");
753-
if (rename(rlogready,rlogdone)<0)
754-
ereport(WARNING,
755-
(errcode_for_file_access(),
756-
errmsg("could not rename file \"%s\" to \"%s\": %m",
757-
rlogready,rlogdone)));
753+
(void)durable_rename(rlogready,rlogdone,WARNING);
758754
}

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