Fsync directory after creating or unlinking file.

If file was created/deleted just before powerloss it's possible that
file system will miss that. To prevent it, call fsync() where creating/
unlinkg file is critical.

Author: Michael Paquier
Reviewed-by: Ashutosh Bapat, Takayuki Tsunakawa, me

src/backend/access/transam/twophase.c

@@ -1650,6 +1650,14 @@ CheckPointTwoPhase(XLogRecPtr redo_horizon)
 	}
 	LWLockRelease(TwoPhaseStateLock);
 
+	/*
+	 * Flush unconditionally the parent directory to make any information
+	 * durable on disk.  Two-phase files could have been removed and those
+	 * removals need to be made persistent as well as any files newly created
+	 * previously since the last checkpoint.
+	 */
+	fsync_fname(TWOPHASE_DIR, true);
+
 	TRACE_POSTGRESQL_TWOPHASE_CHECKPOINT_DONE();
 
 	if (log_checkpoints && serialized_xacts > 0)