Sync PG_VERSION file in CREATE DATABASE.

An OS crash could leave PG_VERSION empty or missing.  The same symptom
appeared in a backup by block device snapshot, taken after the next
checkpoint and before the OS flushes the PG_VERSION blocks.  Device
snapshots are not a documented backup method, however.  Back-patch to
v15, where commit 9c08aea6a3090a396be334cc58c511edab05776a introduced
STRATEGY=WAL_LOG and made it the default.

Discussion: https://postgr.es/m/20240130195003.0a.nmisch@google.com

diff --git a/src/backend/commands/dbcommands.c b/src/backend/commands/dbcommands.c
index dc420acae92c869478ccb096e4873018039cee72..41ed2d3bd9b45a1f828aaccf01e806127ce2d346 100644 (file)
--- a/src/backend/commands/dbcommands.c
+++ b/src/backend/commands/dbcommands.c
@@ -508,6 +508,14 @@ CreateDirAndVersionFile(char *dbpath, Oid dbid, Oid tsid, bool isRedo)
        }
        pgstat_report_wait_end();
 
+       pgstat_report_wait_start(WAIT_EVENT_VERSION_FILE_SYNC);
+       if (pg_fsync(fd) != 0)
+               ereport(data_sync_elevel(ERROR),
+                               (errcode_for_file_access(),
+                                errmsg("could not fsync file \"%s\": %m", versionfile)));
+       fsync_fname(dbpath, true);
+       pgstat_report_wait_end();
+
        /* Close the version file. */
        CloseTransientFile(fd);
 

diff --git a/src/backend/utils/activity/wait_event_names.txt b/src/backend/utils/activity/wait_event_names.txt
index cd22dca7021e3a3d757a7e7a1d687b89de20037d..6464386b77906e6d6ad7227da59a05502e958d05 100644 (file)
--- a/src/backend/utils/activity/wait_event_names.txt
+++ b/src/backend/utils/activity/wait_event_names.txt
@@ -236,6 +236,7 @@ TIMELINE_HISTORY_WRITE      "Waiting for a write of a newly created timeline history
 TWOPHASE_FILE_READ     "Waiting for a read of a two phase state file."
 TWOPHASE_FILE_SYNC     "Waiting for a two phase state file to reach durable storage."
 TWOPHASE_FILE_WRITE    "Waiting for a write of a two phase state file."
+VERSION_FILE_SYNC      "Waiting for the version file to reach durable storage while creating a database."
 VERSION_FILE_WRITE     "Waiting for the version file to be written while creating a database."
 WALSENDER_TIMELINE_HISTORY_READ        "Waiting for a read from a timeline history file during a walsender timeline command."
 WAL_BOOTSTRAP_SYNC     "Waiting for WAL to reach durable storage during bootstrapping."