From a62714fae23d2056242bb2ac872111cab8f9fbd1 Mon Sep 17 00:00:00 2001 From: Andres Freund Date: Wed, 9 Mar 2016 18:53:54 -0800 Subject: [PATCH] Avoid unlikely data-loss scenarios due to rename() without fsync. Renaming a file using rename(2) is not guaranteed to be durable in face of 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 seems better to err on the side of too much durability. The most prominent known case where the previously missing fsyncs could cause data loss is crashes at the end of a checkpoint. After the actual checkpoint has been performed, old WAL files are recycled. When they're filled, their contents are fdatasynced, but we did not fsync the containing directory. An OS/hardware crash in an unfortunate moment could then end up leaving that file with its old name, but new content; WAL replay would thus not replay it. Reported-By: Tomas Vondra Author: Michael Paquier, Tomas Vondra, Andres Freund Discussion: 56583BDD.9060302@2ndquadrant.com Backpatch: All supported branches --- .../pg_stat_statements/pg_stat_statements.c | 6 +- src/backend/access/transam/xlog.c | 66 ++++--------------- src/backend/postmaster/pgarch.c | 6 +- 3 files changed, 13 insertions(+), 65 deletions(-) diff --git a/contrib/pg_stat_statements/pg_stat_statements.c b/contrib/pg_stat_statements/pg_stat_statements.c index 5793068446d..18d501348c3 100644 --- a/contrib/pg_stat_statements/pg_stat_statements.c +++ b/contrib/pg_stat_statements/pg_stat_statements.c @@ -504,11 +504,7 @@ pgss_shmem_shutdown(int code, Datum arg) /* * Rename file into place, so we atomically replace the old one. */ - if (rename(PGSS_DUMP_FILE ".tmp", PGSS_DUMP_FILE) != 0) - ereport(LOG, - (errcode_for_file_access(), - errmsg("could not rename pg_stat_statement file \"%s\": %m", - PGSS_DUMP_FILE ".tmp"))); + (void) durable_rename(PGSS_DUMP_FILE ".tmp", PGSS_DUMP_FILE, LOG); return; diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 3e619c81e25..1e79ebdc8fb 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -2672,34 +2672,16 @@ InstallXLogFileSegment(uint32 *log, uint32 *seg, char *tmppath, } /* - * Prefer link() to rename() here just to be really sure that we don't - * overwrite an existing logfile. However, there shouldn't be one, so - * rename() is an acceptable substitute except for the truly paranoid. + * Perform the rename using link if available, paranoidly trying to avoid + * overwriting an existing file (there shouldn't be one). */ -#if HAVE_WORKING_LINK - if (link(tmppath, path) < 0) + if (durable_link_or_rename(tmppath, path, LOG) != 0) { if (use_lock) LWLockRelease(ControlFileLock); - ereport(LOG, - (errcode_for_file_access(), - errmsg("could not link file \"%s\" to \"%s\" (initialization of log file %u, segment %u): %m", - tmppath, path, *log, *seg))); + /* durable_link_or_rename already emitted log message */ return false; } - unlink(tmppath); -#else - if (rename(tmppath, path) < 0) - { - if (use_lock) - LWLockRelease(ControlFileLock); - ereport(LOG, - (errcode_for_file_access(), - errmsg("could not rename file \"%s\" to \"%s\" (initialization of log file %u, segment %u): %m", - tmppath, path, *log, *seg))); - return false; - } -#endif if (use_lock) LWLockRelease(ControlFileLock); @@ -4620,24 +4602,10 @@ writeTimeLineHistory(TimeLineID newTLI, TimeLineID parentTLI, TLHistoryFilePath(path, newTLI); /* - * Prefer link() to rename() here just to be really sure that we don't - * overwrite an existing logfile. However, there shouldn't be one, so - * rename() is an acceptable substitute except for the truly paranoid. + * Perform the rename using link if available, paranoidly trying to avoid + * overwriting an existing file (there shouldn't be one). */ -#if HAVE_WORKING_LINK - if (link(tmppath, path) < 0) - ereport(ERROR, - (errcode_for_file_access(), - errmsg("could not link file \"%s\" to \"%s\": %m", - tmppath, path))); - unlink(tmppath); -#else - if (rename(tmppath, path) < 0) - ereport(ERROR, - (errcode_for_file_access(), - errmsg("could not rename file \"%s\" to \"%s\": %m", - tmppath, path))); -#endif + durable_link_or_rename(tmppath, path, ERROR); /* The history file can be archived immediately. */ if (XLogArchivingActive()) @@ -5595,11 +5563,7 @@ exitArchiveRecovery(TimeLineID endTLI, uint32 endLogId, uint32 endLogSeg) (errmsg_internal("moving last restored xlog to \"%s\"", xlogpath))); unlink(xlogpath); /* might or might not exist */ - if (rename(recoveryPath, xlogpath) != 0) - ereport(FATAL, - (errcode_for_file_access(), - errmsg("could not rename file \"%s\" to \"%s\": %m", - recoveryPath, xlogpath))); + durable_rename(recoveryPath, xlogpath, FATAL); /* XXX might we need to fix permissions on the file? */ } else @@ -5648,11 +5612,7 @@ exitArchiveRecovery(TimeLineID endTLI, uint32 endLogId, uint32 endLogSeg) * re-enter archive recovery mode in a subsequent crash. */ unlink(RECOVERY_COMMAND_DONE); - if (rename(RECOVERY_COMMAND_FILE, RECOVERY_COMMAND_DONE) != 0) - ereport(FATAL, - (errcode_for_file_access(), - errmsg("could not rename file \"%s\" to \"%s\": %m", - RECOVERY_COMMAND_FILE, RECOVERY_COMMAND_DONE))); + durable_rename(RECOVERY_COMMAND_FILE, RECOVERY_COMMAND_DONE, FATAL); ereport(LOG, (errmsg("archive recovery complete"))); @@ -6548,11 +6508,7 @@ StartupXLOG(void) if (haveBackupLabel) { unlink(BACKUP_LABEL_OLD); - if (rename(BACKUP_LABEL_FILE, BACKUP_LABEL_OLD) != 0) - ereport(FATAL, - (errcode_for_file_access(), - errmsg("could not rename file \"%s\" to \"%s\": %m", - BACKUP_LABEL_FILE, BACKUP_LABEL_OLD))); + durable_rename(BACKUP_LABEL_FILE, BACKUP_LABEL_OLD, FATAL); } /* Check that the GUCs used to generate the WAL allow recovery */ @@ -10148,7 +10104,7 @@ CancelBackup(void) /* remove leftover file from previously canceled backup if it exists */ unlink(BACKUP_LABEL_OLD); - if (rename(BACKUP_LABEL_FILE, BACKUP_LABEL_OLD) == 0) + if (durable_rename(BACKUP_LABEL_FILE, BACKUP_LABEL_OLD, DEBUG1) == 0) { ereport(LOG, (errmsg("online backup mode canceled"), diff --git a/src/backend/postmaster/pgarch.c b/src/backend/postmaster/pgarch.c index 212432ec06b..c7596a949a3 100644 --- a/src/backend/postmaster/pgarch.c +++ b/src/backend/postmaster/pgarch.c @@ -709,9 +709,5 @@ pgarch_archiveDone(char *xlog) StatusFilePath(rlogready, xlog, ".ready"); StatusFilePath(rlogdone, xlog, ".done"); - if (rename(rlogready, rlogdone) < 0) - ereport(WARNING, - (errcode_for_file_access(), - errmsg("could not rename file \"%s\" to \"%s\": %m", - rlogready, rlogdone))); + (void) durable_rename(rlogready, rlogdone, WARNING); }