Remove XLogFileInit() ability to unlink a pre-existing file.

nmisch · michaelpq · commit b494640e8297 · 2025-04-06T14:46:31.000+09:00
Only initdb used it. initdb refuses to operate on a non-empty directory and generally does not cope with pre-existing files of other kinds. Hence, use the opportunity to simplify. This commit has been applied as of 421484f in v15 and newer versions. This is required on stable branches of v13 and v14 to fix a regression reported by Noah Misch, introduced by 1f95181, causing spurious failures in archive recovery (neither streaming nor archive recovery) with concurrent restartpoints. The backpatched versions of the patches have been aligned on these branches by me, Noah Misch is the author. Tests have been conducted by the both of us. Reported-by: Arun Thirupathi Author: Noah Misch <noah@leadboat.com> Discussion: https://postgr.es/m/20210202151416.GB3304930@rfd.leadboat.com Discussion: https://postgr.es/m/20250306193013.36.nmisch@google.com Backpatch-through: 13
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
@@ -2452,7 +2452,7 @@ XLogWrite(XLogwrtRqst WriteRqst, bool flexible)
 	bool		ispartialpage;
 	bool		last_iteration;
 	bool		finishing_seg;
-	bool		use_existent;
+	bool		added;
 	int			curridx;
 	int			npages;
 	int			startidx;
@@ -2518,8 +2518,7 @@ XLogWrite(XLogwrtRqst WriteRqst, bool flexible)
 							wal_segment_size);
 
 			/* create/use new log file */
-			use_existent = true;
-			openLogFile = XLogFileInit(openLogSegNo, &use_existent);
+			openLogFile = XLogFileInit(openLogSegNo, &added);
 			ReserveExternalFD();
 		}
 
@@ -3288,9 +3287,7 @@ XLogNeedsFlush(XLogRecPtr record)
  *
  * logsegno: identify segment to be created/opened.
  *
- * *use_existent: if true, OK to use a pre-existing file (else, any
- * pre-existing file will be deleted).  On return, false iff this call added
- * some segment on disk.
+ * *added: on return, true if this call raised the number of extant segments.
  *
  * Returns FD of opened file.
  *
@@ -3300,7 +3297,7 @@ XLogNeedsFlush(XLogRecPtr record)
  * in a critical section.
  */
 int
-XLogFileInit(XLogSegNo logsegno, bool *use_existent)
+XLogFileInit(XLogSegNo logsegno, bool *added)
 {
 	char		path[MAXPGPATH];
 	char		tmppath[MAXPGPATH];
@@ -3315,19 +3312,17 @@ XLogFileInit(XLogSegNo logsegno, bool *use_existent)
 	/*
 	 * Try to use existent file (checkpoint maker may have created it already)
 	 */
-	if (*use_existent)
+	*added = false;
+	fd = BasicOpenFile(path, O_RDWR | PG_BINARY | get_sync_bit(sync_method));
+	if (fd < 0)
 	{
-		fd = BasicOpenFile(path, O_RDWR | PG_BINARY | get_sync_bit(sync_method));
-		if (fd < 0)
-		{
-			if (errno != ENOENT)
-				ereport(ERROR,
-						(errcode_for_file_access(),
-						 errmsg("could not open file \"%s\": %m", path)));
-		}
-		else
-			return fd;
+		if (errno != ENOENT)
+			ereport(ERROR,
+					(errcode_for_file_access(),
+					 errmsg("could not open file \"%s\": %m", path)));
 	}
+	else
+		return fd;
 
 	/*
 	 * Initialize an empty (all zeroes) segment.  NOTE: it is possible that
@@ -3440,12 +3435,9 @@ XLogFileInit(XLogSegNo logsegno, bool *use_existent)
 				 errmsg("could not close file \"%s\": %m", tmppath)));
 
 	/*
-	 * Now move the segment into place with its final name.
-	 *
-	 * If caller didn't want to use a pre-existing file, get rid of any
-	 * pre-existing file.  Otherwise, cope with possibility that someone else
-	 * has created the file while we were filling ours: if so, use ours to
-	 * pre-create a future log segment.
+	 * Now move the segment into place with its final name.  Cope with
+	 * possibility that someone else has created the file while we were
+	 * filling ours: if so, use ours to pre-create a future log segment.
 	 */
 	installed_segno = logsegno;
 
@@ -3459,9 +3451,8 @@ XLogFileInit(XLogSegNo logsegno, bool *use_existent)
 	 * CheckPointSegments.
 	 */
 	max_segno = logsegno + CheckPointSegments;
-	if (InstallXLogFileSegment(&installed_segno, tmppath,
-							   *use_existent, max_segno))
-		*use_existent = false;
+	if (InstallXLogFileSegment(&installed_segno, tmppath, true, max_segno))
+		*added = true;
 	else
 	{
 		/*
@@ -3946,18 +3937,17 @@ PreallocXlogFiles(XLogRecPtr endptr)
 {
 	XLogSegNo	_logSegNo;
 	int			lf;
-	bool		use_existent;
+	bool		added;
 	uint64		offset;
 
 	XLByteToPrevSeg(endptr, _logSegNo, wal_segment_size);
 	offset = XLogSegmentOffset(endptr - 1, wal_segment_size);
 	if (offset >= (uint32) (0.75 * wal_segment_size))
 	{
 		_logSegNo++;
-		use_existent = true;
-		lf = XLogFileInit(_logSegNo, &use_existent);
+		lf = XLogFileInit(_logSegNo, &added);
 		close(lf);
-		if (!use_existent)
+		if (added)
 			CheckpointStats.ckpt_segs_added++;
 	}
 }
@@ -5271,7 +5261,7 @@ BootStrapXLOG(void)
 	XLogLongPageHeader longpage;
 	XLogRecord *record;
 	char	   *recptr;
-	bool		use_existent;
+	bool		added;
 	uint64		sysidentifier;
 	struct timeval tv;
 	pg_crc32c	crc;
@@ -5368,8 +5358,7 @@ BootStrapXLOG(void)
 	record->xl_crc = crc;
 
 	/* Create first XLOG segment file */
-	use_existent = false;
-	openLogFile = XLogFileInit(1, &use_existent);
+	openLogFile = XLogFileInit(1, &added);
 
 	/*
 	 * We needn't bother with Reserve/ReleaseExternalFD here, since we'll
@@ -5675,10 +5664,10 @@ exitArchiveRecovery(TimeLineID endTLI, XLogRecPtr endOfLog)
 		 * The switch happened at a segment boundary, so just create the next
 		 * segment on the new timeline.
 		 */
-		bool		use_existent = true;
+		bool		added;
 		int			fd;
 
-		fd = XLogFileInit(startLogSegNo, &use_existent);
+		fd = XLogFileInit(startLogSegNo, &added);
 
 		if (close(fd) != 0)
 		{
diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c
@@ -890,11 +890,11 @@ XLogWalRcvWrite(char *buf, Size nbytes, XLogRecPtr recptr)
 
 		if (recvFile < 0)
 		{
-			bool		use_existent = true;
+			bool		added = true;
 
 			/* Create/use new log file */
 			XLByteToSeg(recptr, recvSegNo, wal_segment_size);
-			recvFile = XLogFileInit(recvSegNo, &use_existent);
+			recvFile = XLogFileInit(recvSegNo, &added);
 			recvFileTLI = ThisTimeLineID;
 		}
 
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
@@ -296,7 +296,7 @@ extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
 extern void XLogFlush(XLogRecPtr RecPtr);
 extern bool XLogBackgroundFlush(void);
 extern bool XLogNeedsFlush(XLogRecPtr RecPtr);
-extern int	XLogFileInit(XLogSegNo segno, bool *use_existent);
+extern int	XLogFileInit(XLogSegNo segno, bool *added);
 extern int	XLogFileOpen(XLogSegNo segno);
 
 extern void CheckXLogRemoved(XLogSegNo segno, TimeLineID tli);

Original file line number	Diff line number	Diff line change
`@@ -890,11 +890,11 @@ XLogWalRcvWrite(char *buf, Size nbytes, XLogRecPtr recptr)`
`890`	`890`
`891`	`891`	`if (recvFile < 0)`
`892`	`892`	`{`
`893`		`- bool use_existent = true;`
	`893`	`+ bool added = true;`
`894`	`894`
`895`	`895`	`/* Create/use new log file */`
`896`	`896`	`XLByteToSeg(recptr, recvSegNo, wal_segment_size);`
`897`		`- recvFile = XLogFileInit(recvSegNo, &use_existent);`
	`897`	`+ recvFile = XLogFileInit(recvSegNo, &added);`
`898`	`898`	`recvFileTLI = ThisTimeLineID;`
`899`	`899`	`}`
`900`	`900`