3 files changed, 16 insertions, 21 deletions

diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index b715152e8d0..321da9f5f67 100644
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -1735,8 +1735,8 @@ restoreTwoPhaseData(void)
 	DIR		   *cldir;
 	struct dirent *clde;
 
-	cldir = AllocateDir(TWOPHASE_DIR);
 	LWLockAcquire(TwoPhaseStateLock, LW_EXCLUSIVE);
+	cldir = AllocateDir(TWOPHASE_DIR);
 	while ((clde = ReadDir(cldir, TWOPHASE_DIR)) != NULL)
 	{
 		if (strlen(clde->d_name) == 8 &&
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index fba201f6599..a11406c741c 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -3764,10 +3764,16 @@ PreallocXlogFiles(XLogRecPtr endptr)
  * existed while the server has been running, as this function always
  * succeeds if no WAL segments have been removed since startup.
  * 'tli' is only used in the error message.
+ *
+ * Note: this function guarantees to keep errno unchanged on return.
+ * This supports callers that use this to possibly deliver a better
+ * error message about a missing file, while still being able to throw
+ * a normal file-access error afterwards, if this does return.
  */
 void
 CheckXLogRemoved(XLogSegNo segno, TimeLineID tli)
 {
+	int			save_errno = errno;
 	XLogSegNo	lastRemovedSegNo;
 
 	SpinLockAcquire(&XLogCtl->info_lck);
@@ -3779,11 +3785,13 @@ CheckXLogRemoved(XLogSegNo segno, TimeLineID tli)
 		char		filename[MAXFNAMELEN];
 
 		XLogFileName(filename, tli, segno, wal_segment_size);
+		errno = save_errno;
 		ereport(ERROR,
 				(errcode_for_file_access(),
 				 errmsg("requested WAL segment %s has already been removed",
 						filename)));
 	}
+	errno = save_errno;
 }
 
 /*
@@ -3837,13 +3845,6 @@ RemoveOldXlogFiles(XLogSegNo segno, XLogRecPtr PriorRedoPtr, XLogRecPtr endptr)
 	struct dirent *xlde;
 	char		lastoff[MAXFNAMELEN];
 
-	xldir = AllocateDir(XLOGDIR);
-	if (xldir == NULL)
-		ereport(ERROR,
-				(errcode_for_file_access(),
-				 errmsg("could not open write-ahead log directory \"%s\": %m",
-						XLOGDIR)));
-
 	/*
 	 * Construct a filename of the last segment to be kept. The timeline ID
 	 * doesn't matter, we ignore that in the comparison. (During recovery,
@@ -3854,6 +3855,8 @@ RemoveOldXlogFiles(XLogSegNo segno, XLogRecPtr PriorRedoPtr, XLogRecPtr endptr)
 	elog(DEBUG2, "attempting to remove WAL segments older than log file %s",
 		 lastoff);
 
+	xldir = AllocateDir(XLOGDIR);
+
 	while ((xlde = ReadDir(xldir, XLOGDIR)) != NULL)
 	{
 		/* Ignore files that are not XLOG segments */
@@ -3912,13 +3915,6 @@ RemoveNonParentXlogFiles(XLogRecPtr switchpoint, TimeLineID newTLI)
 
 	XLByteToPrevSeg(switchpoint, endLogSegNo, wal_segment_size);
 
-	xldir = AllocateDir(XLOGDIR);
-	if (xldir == NULL)
-		ereport(ERROR,
-				(errcode_for_file_access(),
-				 errmsg("could not open write-ahead log directory \"%s\": %m",
-						XLOGDIR)));
-
 	/*
 	 * Construct a filename of the last segment to be kept.
 	 */
@@ -3927,6 +3923,8 @@ RemoveNonParentXlogFiles(XLogRecPtr switchpoint, TimeLineID newTLI)
 	elog(DEBUG2, "attempting to remove WAL segments newer than log file %s",
 		 switchseg);
 
+	xldir = AllocateDir(XLOGDIR);
+
 	while ((xlde = ReadDir(xldir, XLOGDIR)) != NULL)
 	{
 		/* Ignore files that are not XLOG segments */
@@ -4108,11 +4106,6 @@ CleanupBackupHistory(void)
 	char		path[MAXPGPATH + sizeof(XLOGDIR)];
 
 	xldir = AllocateDir(XLOGDIR);
-	if (xldir == NULL)
-		ereport(ERROR,
-				(errcode_for_file_access(),
-				 errmsg("could not open write-ahead log directory \"%s\": %m",
-						XLOGDIR)));
 
 	while ((xlde = ReadDir(xldir, XLOGDIR)) != NULL)
 	{
diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c
index 443ccd64112..48d85c1ce5d 100644
--- a/src/backend/access/transam/xlogfuncs.c
+++ b/src/backend/access/transam/xlogfuncs.c
@@ -89,7 +89,9 @@ pg_start_backup(PG_FUNCTION_ARGS)
 	dir = AllocateDir("pg_tblspc");
 	if (!dir)
 		ereport(ERROR,
-				(errmsg("could not open directory \"%s\": %m", "pg_tblspc")));
+				(errcode_for_file_access(),
+				 errmsg("could not open directory \"%s\": %m",
+						"pg_tblspc")));
 
 	if (exclusive)
 	{