diff --git a/contrib/pg_stat_statements/pg_stat_statements.c b/contrib/pg_stat_statements/pg_stat_statements.c
index fa409d72b7..3ab1fd2db4 100644
--- a/contrib/pg_stat_statements/pg_stat_statements.c
+++ b/contrib/pg_stat_statements/pg_stat_statements.c
@@ -1869,8 +1869,7 @@ qtext_store(const char *query, int query_len,
 	*query_offset = off;
 
 	/* Now write the data into the successfully-reserved part of the file */
-	fd = OpenTransientFile(PGSS_TEXT_FILE, O_RDWR | O_CREAT | PG_BINARY,
-						   S_IRUSR | S_IWUSR);
+	fd = OpenTransientFile(PGSS_TEXT_FILE, O_RDWR | O_CREAT | PG_BINARY);
 	if (fd < 0)
 		goto error;
 
@@ -1934,7 +1933,7 @@ qtext_load_file(Size *buffer_size)
 	int			fd;
 	struct stat stat;
 
-	fd = OpenTransientFile(PGSS_TEXT_FILE, O_RDONLY | PG_BINARY, 0);
+	fd = OpenTransientFile(PGSS_TEXT_FILE, O_RDONLY | PG_BINARY);
 	if (fd < 0)
 	{
 		if (errno != ENOENT)
diff --git a/src/backend/access/heap/rewriteheap.c b/src/backend/access/heap/rewriteheap.c
index bd560e47e1..f93c194e18 100644
--- a/src/backend/access/heap/rewriteheap.c
+++ b/src/backend/access/heap/rewriteheap.c
@@ -1013,8 +1013,7 @@ logical_rewrite_log_mapping(RewriteState state, TransactionId xid,
 		src->off = 0;
 		memcpy(src->path, path, sizeof(path));
 		src->vfd = PathNameOpenFile(path,
-									O_CREAT | O_EXCL | O_WRONLY | PG_BINARY,
-									S_IRUSR | S_IWUSR);
+									O_CREAT | O_EXCL | O_WRONLY | PG_BINARY);
 		if (src->vfd < 0)
 			ereport(ERROR,
 					(errcode_for_file_access(),
@@ -1133,8 +1132,7 @@ heap_xlog_logical_rewrite(XLogReaderState *r)
 			 xlrec->mapped_xid, XLogRecGetXid(r));
 
 	fd = OpenTransientFile(path,
-						   O_CREAT | O_WRONLY | PG_BINARY,
-						   S_IRUSR | S_IWUSR);
+						   O_CREAT | O_WRONLY | PG_BINARY);
 	if (fd < 0)
 		ereport(ERROR,
 				(errcode_for_file_access(),
@@ -1258,7 +1256,7 @@ CheckPointLogicalRewriteHeap(void)
 		}
 		else
 		{
-			int			fd = OpenTransientFile(path, O_RDONLY | PG_BINARY, 0);
+			int			fd = OpenTransientFile(path, O_RDONLY | PG_BINARY);
 
 			/*
 			 * The file cannot vanish due to concurrency since this function
diff --git a/src/backend/access/transam/slru.c b/src/backend/access/transam/slru.c
index 77edc51e1c..9dd77190ec 100644
--- a/src/backend/access/transam/slru.c
+++ b/src/backend/access/transam/slru.c
@@ -599,7 +599,7 @@ SimpleLruDoesPhysicalPageExist(SlruCtl ctl, int pageno)
 
 	SlruFileName(ctl, path, segno);
 
-	fd = OpenTransientFile(path, O_RDWR | PG_BINARY, S_IRUSR | S_IWUSR);
+	fd = OpenTransientFile(path, O_RDWR | PG_BINARY);
 	if (fd < 0)
 	{
 		/* expected: file doesn't exist */
@@ -654,7 +654,7 @@ SlruPhysicalReadPage(SlruCtl ctl, int pageno, int slotno)
 	 * SlruPhysicalWritePage).  Hence, if we are InRecovery, allow the case
 	 * where the file doesn't exist, and return zeroes instead.
 	 */
-	fd = OpenTransientFile(path, O_RDWR | PG_BINARY, S_IRUSR | S_IWUSR);
+	fd = OpenTransientFile(path, O_RDWR | PG_BINARY);
 	if (fd < 0)
 	{
 		if (errno != ENOENT || !InRecovery)
@@ -804,8 +804,7 @@ SlruPhysicalWritePage(SlruCtl ctl, int pageno, int slotno, SlruFlush fdata)
 		 * don't use O_EXCL or O_TRUNC or anything like that.
 		 */
 		SlruFileName(ctl, path, segno);
-		fd = OpenTransientFile(path, O_RDWR | O_CREAT | PG_BINARY,
-							   S_IRUSR | S_IWUSR);
+		fd = OpenTransientFile(path, O_RDWR | O_CREAT | PG_BINARY);
 		if (fd < 0)
 		{
 			slru_errcause = SLRU_OPEN_FAILED;
diff --git a/src/backend/access/transam/timeline.c b/src/backend/access/transam/timeline.c
index 63db8a981d..3d65e5624a 100644
--- a/src/backend/access/transam/timeline.c
+++ b/src/backend/access/transam/timeline.c
@@ -307,8 +307,7 @@ writeTimeLineHistory(TimeLineID newTLI, TimeLineID parentTLI,
 	unlink(tmppath);
 
 	/* do not use get_sync_bit() here --- want to fsync only at end of fill */
-	fd = OpenTransientFile(tmppath, O_RDWR | O_CREAT | O_EXCL,
-						   S_IRUSR | S_IWUSR);
+	fd = OpenTransientFile(tmppath, O_RDWR | O_CREAT | O_EXCL);
 	if (fd < 0)
 		ereport(ERROR,
 				(errcode_for_file_access(),
@@ -325,7 +324,7 @@ writeTimeLineHistory(TimeLineID newTLI, TimeLineID parentTLI,
 	else
 		TLHistoryFilePath(path, parentTLI);
 
-	srcfd = OpenTransientFile(path, O_RDONLY, 0);
+	srcfd = OpenTransientFile(path, O_RDONLY);
 	if (srcfd < 0)
 	{
 		if (errno != ENOENT)
@@ -459,8 +458,7 @@ writeTimeLineHistoryFile(TimeLineID tli, char *content, int size)
 	unlink(tmppath);
 
 	/* do not use get_sync_bit() here --- want to fsync only at end of fill */
-	fd = OpenTransientFile(tmppath, O_RDWR | O_CREAT | O_EXCL,
-						   S_IRUSR | S_IWUSR);
+	fd = OpenTransientFile(tmppath, O_RDWR | O_CREAT | O_EXCL);
 	if (fd < 0)
 		ereport(ERROR,
 				(errcode_for_file_access(),
diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index bfd800bc16..cfaf8da781 100644
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -1195,7 +1195,7 @@ ReadTwoPhaseFile(TransactionId xid, bool give_warnings)
 
 	TwoPhaseFilePath(path, xid);
 
-	fd = OpenTransientFile(path, O_RDONLY | PG_BINARY, 0);
+	fd = OpenTransientFile(path, O_RDONLY | PG_BINARY);
 	if (fd < 0)
 	{
 		if (give_warnings)
@@ -1581,8 +1581,7 @@ RecreateTwoPhaseFile(TransactionId xid, void *content, int len)
 	TwoPhaseFilePath(path, xid);
 
 	fd = OpenTransientFile(path,
-						   O_CREAT | O_TRUNC | O_WRONLY | PG_BINARY,
-						   S_IRUSR | S_IWUSR);
+						   O_CREAT | O_TRUNC | O_WRONLY | PG_BINARY);
 	if (fd < 0)
 		ereport(ERROR,
 				(errcode_for_file_access(),
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 051347163b..dd028a12a4 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -3185,8 +3185,7 @@ XLogFileInit(XLogSegNo logsegno, bool *use_existent, bool use_lock)
 	 */
 	if (*use_existent)
 	{
-		fd = BasicOpenFile(path, O_RDWR | PG_BINARY | get_sync_bit(sync_method),
-						   S_IRUSR | S_IWUSR);
+		fd = BasicOpenFile(path, O_RDWR | PG_BINARY | get_sync_bit(sync_method));
 		if (fd < 0)
 		{
 			if (errno != ENOENT)
@@ -3211,8 +3210,7 @@ XLogFileInit(XLogSegNo logsegno, bool *use_existent, bool use_lock)
 	unlink(tmppath);
 
 	/* do not use get_sync_bit() here --- want to fsync only at end of fill */
-	fd = BasicOpenFile(tmppath, O_RDWR | O_CREAT | O_EXCL | PG_BINARY,
-					   S_IRUSR | S_IWUSR);
+	fd = BasicOpenFile(tmppath, O_RDWR | O_CREAT | O_EXCL | PG_BINARY);
 	if (fd < 0)
 		ereport(ERROR,
 				(errcode_for_file_access(),
@@ -3308,8 +3306,7 @@ XLogFileInit(XLogSegNo logsegno, bool *use_existent, bool use_lock)
 	*use_existent = false;
 
 	/* Now open original target segment (might not be file I just made) */
-	fd = BasicOpenFile(path, O_RDWR | PG_BINARY | get_sync_bit(sync_method),
-					   S_IRUSR | S_IWUSR);
+	fd = BasicOpenFile(path, O_RDWR | PG_BINARY | get_sync_bit(sync_method));
 	if (fd < 0)
 		ereport(ERROR,
 				(errcode_for_file_access(),
@@ -3350,7 +3347,7 @@ XLogFileCopy(XLogSegNo destsegno, TimeLineID srcTLI, XLogSegNo srcsegno,
 	 * Open the source file
 	 */
 	XLogFilePath(path, srcTLI, srcsegno, wal_segment_size);
-	srcfd = OpenTransientFile(path, O_RDONLY | PG_BINARY, 0);
+	srcfd = OpenTransientFile(path, O_RDONLY | PG_BINARY);
 	if (srcfd < 0)
 		ereport(ERROR,
 				(errcode_for_file_access(),
@@ -3364,8 +3361,7 @@ XLogFileCopy(XLogSegNo destsegno, TimeLineID srcTLI, XLogSegNo srcsegno,
 	unlink(tmppath);
 
 	/* do not use get_sync_bit() here --- want to fsync only at end of fill */
-	fd = OpenTransientFile(tmppath, O_RDWR | O_CREAT | O_EXCL | PG_BINARY,
-						   S_IRUSR | S_IWUSR);
+	fd = OpenTransientFile(tmppath, O_RDWR | O_CREAT | O_EXCL | PG_BINARY);
 	if (fd < 0)
 		ereport(ERROR,
 				(errcode_for_file_access(),
@@ -3543,8 +3539,7 @@ XLogFileOpen(XLogSegNo segno)
 
 	XLogFilePath(path, ThisTimeLineID, segno, wal_segment_size);
 
-	fd = BasicOpenFile(path, O_RDWR | PG_BINARY | get_sync_bit(sync_method),
-					   S_IRUSR | S_IWUSR);
+	fd = BasicOpenFile(path, O_RDWR | PG_BINARY | get_sync_bit(sync_method));
 	if (fd < 0)
 		ereport(PANIC,
 				(errcode_for_file_access(),
@@ -3610,7 +3605,7 @@ XLogFileRead(XLogSegNo segno, int emode, TimeLineID tli,
 		snprintf(path, MAXPGPATH, XLOGDIR "/%s", xlogfname);
 	}
 
-	fd = BasicOpenFile(path, O_RDONLY | PG_BINARY, 0);
+	fd = BasicOpenFile(path, O_RDONLY | PG_BINARY);
 	if (fd >= 0)
 	{
 		/* Success! */
@@ -4449,8 +4444,7 @@ WriteControlFile(void)
 	memcpy(buffer, ControlFile, sizeof(ControlFileData));
 
 	fd = BasicOpenFile(XLOG_CONTROL_FILE,
-					   O_RDWR | O_CREAT | O_EXCL | PG_BINARY,
-					   S_IRUSR | S_IWUSR);
+					   O_RDWR | O_CREAT | O_EXCL | PG_BINARY);
 	if (fd < 0)
 		ereport(PANIC,
 				(errcode_for_file_access(),
@@ -4494,8 +4488,7 @@ ReadControlFile(void)
 	 * Read data...
 	 */
 	fd = BasicOpenFile(XLOG_CONTROL_FILE,
-					   O_RDWR | PG_BINARY,
-					   S_IRUSR | S_IWUSR);
+					   O_RDWR | PG_BINARY);
 	if (fd < 0)
 		ereport(PANIC,
 				(errcode_for_file_access(),
@@ -4695,8 +4688,7 @@ UpdateControlFile(void)
 	FIN_CRC32C(ControlFile->crc);
 
 	fd = BasicOpenFile(XLOG_CONTROL_FILE,
-					   O_RDWR | PG_BINARY,
-					   S_IRUSR | S_IWUSR);
+					   O_RDWR | PG_BINARY);
 	if (fd < 0)
 		ereport(PANIC,
 				(errcode_for_file_access(),
diff --git a/src/backend/access/transam/xlogutils.c b/src/backend/access/transam/xlogutils.c
index b11c94c9b6..3af6e19c98 100644
--- a/src/backend/access/transam/xlogutils.c
+++ b/src/backend/access/transam/xlogutils.c
@@ -694,7 +694,7 @@ XLogRead(char *buf, int segsize, TimeLineID tli, XLogRecPtr startptr,
 
 			XLogFilePath(path, tli, sendSegNo, segsize);
 
-			sendFile = BasicOpenFile(path, O_RDONLY | PG_BINARY, 0);
+			sendFile = BasicOpenFile(path, O_RDONLY | PG_BINARY);
 
 			if (sendFile < 0)
 			{
diff --git a/src/backend/catalog/catalog.c b/src/backend/catalog/catalog.c
index 92d943cac7..f50ae3e41d 100644
--- a/src/backend/catalog/catalog.c
+++ b/src/backend/catalog/catalog.c
@@ -444,7 +444,7 @@ GetNewRelFileNode(Oid reltablespace, Relation pg_class, char relpersistence)
 
 		/* Check for existing file of same name */
 		rpath = relpath(rnode, MAIN_FORKNUM);
-		fd = BasicOpenFile(rpath, O_RDONLY | PG_BINARY, 0);
+		fd = BasicOpenFile(rpath, O_RDONLY | PG_BINARY);
 
 		if (fd >= 0)
 		{
diff --git a/src/backend/libpq/be-fsstubs.c b/src/backend/libpq/be-fsstubs.c
index 19b34bfc84..84c2d26402 100644
--- a/src/backend/libpq/be-fsstubs.c
+++ b/src/backend/libpq/be-fsstubs.c
@@ -462,7 +462,7 @@ lo_import_internal(text *filename, Oid lobjOid)
 	 * open the file to be read in
 	 */
 	text_to_cstring_buffer(filename, fnamebuf, sizeof(fnamebuf));
-	fd = OpenTransientFile(fnamebuf, O_RDONLY | PG_BINARY, S_IRWXU);
+	fd = OpenTransientFile(fnamebuf, O_RDONLY | PG_BINARY);
 	if (fd < 0)
 		ereport(ERROR,
 				(errcode_for_file_access(),
@@ -540,8 +540,8 @@ be_lo_export(PG_FUNCTION_ARGS)
 	oumask = umask(S_IWGRP | S_IWOTH);
 	PG_TRY();
 	{
-		fd = OpenTransientFile(fnamebuf, O_CREAT | O_WRONLY | O_TRUNC | PG_BINARY,
-							   S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
+		fd = OpenTransientFilePerm(fnamebuf, O_CREAT | O_WRONLY | O_TRUNC | PG_BINARY,
+								   S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
 	}
 	PG_CATCH();
 	{
diff --git a/src/backend/replication/logical/origin.c b/src/backend/replication/logical/origin.c
index edc6efb8a6..20d32679e0 100644
--- a/src/backend/replication/logical/origin.c
+++ b/src/backend/replication/logical/origin.c
@@ -546,9 +546,8 @@ CheckPointReplicationOrigin(void)
 	 * no other backend can perform this at the same time, we're protected by
 	 * CheckpointLock.
 	 */
-	tmpfd = OpenTransientFile((char *) tmppath,
-							  O_CREAT | O_EXCL | O_WRONLY | PG_BINARY,
-							  S_IRUSR | S_IWUSR);
+	tmpfd = OpenTransientFile(tmppath,
+							  O_CREAT | O_EXCL | O_WRONLY | PG_BINARY);
 	if (tmpfd < 0)
 		ereport(PANIC,
 				(errcode_for_file_access(),
@@ -660,7 +659,7 @@ StartupReplicationOrigin(void)
 
 	elog(DEBUG2, "starting up replication origin progress state");
 
-	fd = OpenTransientFile((char *) path, O_RDONLY | PG_BINARY, 0);
+	fd = OpenTransientFile(path, O_RDONLY | PG_BINARY);
 
 	/*
 	 * might have had max_replication_slots == 0 last run, or we just brought
diff --git a/src/backend/replication/logical/reorderbuffer.c b/src/backend/replication/logical/reorderbuffer.c
index 68766d522d..0f607bab70 100644
--- a/src/backend/replication/logical/reorderbuffer.c
+++ b/src/backend/replication/logical/reorderbuffer.c
@@ -2104,8 +2104,7 @@ ReorderBufferSerializeTXN(ReorderBuffer *rb, ReorderBufferTXN *txn)
 
 			/* open segment, create it if necessary */
 			fd = OpenTransientFile(path,
-								   O_CREAT | O_WRONLY | O_APPEND | PG_BINARY,
-								   S_IRUSR | S_IWUSR);
+								   O_CREAT | O_WRONLY | O_APPEND | PG_BINARY);
 
 			if (fd < 0)
 				ereport(ERROR,
@@ -2349,7 +2348,7 @@ ReorderBufferRestoreChanges(ReorderBuffer *rb, ReorderBufferTXN *txn,
 					NameStr(MyReplicationSlot->data.name), txn->xid,
 					(uint32) (recptr >> 32), (uint32) recptr);
 
-			*fd = OpenTransientFile(path, O_RDONLY | PG_BINARY, 0);
+			*fd = OpenTransientFile(path, O_RDONLY | PG_BINARY);
 			if (*fd < 0 && errno == ENOENT)
 			{
 				*fd = -1;
@@ -3038,7 +3037,7 @@ ApplyLogicalMappingFile(HTAB *tuplecid_data, Oid relid, const char *fname)
 	LogicalRewriteMappingData map;
 
 	sprintf(path, "pg_logical/mappings/%s", fname);
-	fd = OpenTransientFile(path, O_RDONLY | PG_BINARY, 0);
+	fd = OpenTransientFile(path, O_RDONLY | PG_BINARY);
 	if (fd < 0)
 		ereport(ERROR,
 				(errcode_for_file_access(),
diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c
index fba57a0470..ad65b9831d 100644
--- a/src/backend/replication/logical/snapbuild.c
+++ b/src/backend/replication/logical/snapbuild.c
@@ -1597,8 +1597,7 @@ SnapBuildSerialize(SnapBuild *builder, XLogRecPtr lsn)
 
 	/* we have valid data now, open tempfile and write it there */
 	fd = OpenTransientFile(tmppath,
-						   O_CREAT | O_EXCL | O_WRONLY | PG_BINARY,
-						   S_IRUSR | S_IWUSR);
+						   O_CREAT | O_EXCL | O_WRONLY | PG_BINARY);
 	if (fd < 0)
 		ereport(ERROR,
 				(errmsg("could not open file \"%s\": %m", path)));
@@ -1682,7 +1681,7 @@ SnapBuildRestore(SnapBuild *builder, XLogRecPtr lsn)
 	sprintf(path, "pg_logical/snapshots/%X-%X.snap",
 			(uint32) (lsn >> 32), (uint32) lsn);
 
-	fd = OpenTransientFile(path, O_RDONLY | PG_BINARY, 0);
+	fd = OpenTransientFile(path, O_RDONLY | PG_BINARY);
 
 	if (fd < 0 && errno == ENOENT)
 		return false;
diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
index 23de2577ef..0d27b6f39e 100644
--- a/src/backend/replication/slot.c
+++ b/src/backend/replication/slot.c
@@ -1233,9 +1233,7 @@ SaveSlotToPath(ReplicationSlot *slot, const char *dir, int elevel)
 	sprintf(tmppath, "%s/state.tmp", dir);
 	sprintf(path, "%s/state", dir);
 
-	fd = OpenTransientFile(tmppath,
-						   O_CREAT | O_EXCL | O_WRONLY | PG_BINARY,
-						   S_IRUSR | S_IWUSR);
+	fd = OpenTransientFile(tmppath, O_CREAT | O_EXCL | O_WRONLY | PG_BINARY);
 	if (fd < 0)
 	{
 		ereport(elevel,
@@ -1354,7 +1352,7 @@ RestoreSlotFromDisk(const char *name)
 
 	elog(DEBUG1, "restoring replication slot from \"%s\"", path);
 
-	fd = OpenTransientFile(path, O_RDWR | PG_BINARY, 0);
+	fd = OpenTransientFile(path, O_RDWR | PG_BINARY);
 
 	/*
 	 * We do not need to handle this as we are rename()ing the directory into
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index 56999e9315..6ec4e63161 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -472,7 +472,7 @@ SendTimeLineHistory(TimeLineHistoryCmd *cmd)
 	pq_sendint(&buf, len, 4);	/* col1 len */
 	pq_sendbytes(&buf, histfname, len);
 
-	fd = OpenTransientFile(path, O_RDONLY | PG_BINARY, 0666);
+	fd = OpenTransientFile(path, O_RDONLY | PG_BINARY);
 	if (fd < 0)
 		ereport(ERROR,
 				(errcode_for_file_access(),
@@ -2366,7 +2366,7 @@ retry:
 
 			XLogFilePath(path, curFileTimeLine, sendSegNo, wal_segment_size);
 
-			sendFile = BasicOpenFile(path, O_RDONLY | PG_BINARY, 0);
+			sendFile = BasicOpenFile(path, O_RDONLY | PG_BINARY);
 			if (sendFile < 0)
 			{
 				/*
diff --git a/src/backend/storage/file/copydir.c b/src/backend/storage/file/copydir.c
index 1e2691685a..a5e074ead8 100644
--- a/src/backend/storage/file/copydir.c
+++ b/src/backend/storage/file/copydir.c
@@ -148,14 +148,13 @@ copy_file(char *fromfile, char *tofile)
 	/*
 	 * Open the files
 	 */
-	srcfd = OpenTransientFile(fromfile, O_RDONLY | PG_BINARY, 0);
+	srcfd = OpenTransientFile(fromfile, O_RDONLY | PG_BINARY);
 	if (srcfd < 0)
 		ereport(ERROR,
 				(errcode_for_file_access(),
 				 errmsg("could not open file \"%s\": %m", fromfile)));
 
-	dstfd = OpenTransientFile(tofile, O_RDWR | O_CREAT | O_EXCL | PG_BINARY,
-							  S_IRUSR | S_IWUSR);
+	dstfd = OpenTransientFile(tofile, O_RDWR | O_CREAT | O_EXCL | PG_BINARY);
 	if (dstfd < 0)
 		ereport(ERROR,
 				(errcode_for_file_access(),
diff --git a/src/backend/storage/file/fd.c b/src/backend/storage/file/fd.c
index 83b061a036..b0c174284b 100644
--- a/src/backend/storage/file/fd.c
+++ b/src/backend/storage/file/fd.c
@@ -116,6 +116,11 @@
  */
 #define FD_MINFREE				10
 
+/*
+ * Default mode for created files, unless something else is specified using
+ * the *Perm() function variants.
+ */
+#define PG_FILE_MODE_DEFAULT	(S_IRUSR | S_IWUSR)
 
 /*
  * A number of platforms allow individual processes to open many more files
@@ -186,7 +191,7 @@ typedef struct vfd
 	char	   *fileName;		/* name of file, or NULL for unused VFD */
 	/* NB: fileName is malloc'd, and must be free'd when closing the VFD */
 	int			fileFlags;		/* open(2) flags for (re)opening the file */
-	int			fileMode;		/* mode to pass to open(2) */
+	mode_t		fileMode;		/* mode to pass to open(2) */
 } Vfd;
 
 /*
@@ -604,7 +609,7 @@ durable_rename(const char *oldfile, const char *newfile, int elevel)
 	if (fsync_fname_ext(oldfile, false, false, elevel) != 0)
 		return -1;
 
-	fd = OpenTransientFile((char *) newfile, PG_BINARY | O_RDWR, 0);
+	fd = OpenTransientFile(newfile, PG_BINARY | O_RDWR);
 	if (fd < 0)
 	{
 		if (errno != ENOENT)
@@ -917,7 +922,17 @@ set_max_safe_fds(void)
 }
 
 /*
- * BasicOpenFile --- same as open(2) except can free other FDs if needed
+ * Open a file with BasicOpenFilePerm() and pass default file mode for the
+ * fileMode parameter.
+ */
+int
+BasicOpenFile(const char *fileName, int fileFlags)
+{
+	return BasicOpenFilePerm(fileName, fileFlags, PG_FILE_MODE_DEFAULT);
+}
+
+/*
+ * BasicOpenFilePerm --- same as open(2) except can free other FDs if needed
  *
  * This is exported for use by places that really want a plain kernel FD,
  * but need to be proof against running out of FDs.  Once an FD has been
@@ -933,7 +948,7 @@ set_max_safe_fds(void)
  * this module wouldn't have any open files to close at that point anyway.
  */
 int
-BasicOpenFile(FileName fileName, int fileFlags, int fileMode)
+BasicOpenFilePerm(const char *fileName, int fileFlags, mode_t fileMode)
 {
 	int			fd;
 
@@ -1084,8 +1099,8 @@ LruInsert(File file)
 		 * overall system file table being full.  So, be prepared to release
 		 * another FD if necessary...
 		 */
-		vfdP->fd = BasicOpenFile(vfdP->fileName, vfdP->fileFlags,
-								 vfdP->fileMode);
+		vfdP->fd = BasicOpenFilePerm(vfdP->fileName, vfdP->fileFlags,
+									 vfdP->fileMode);
 		if (vfdP->fd < 0)
 		{
 			DO_DB(elog(LOG, "re-open failed: %m"));
@@ -1292,6 +1307,16 @@ FileInvalidate(File file)
 }
 #endif
 
+/*
+ * Open a file with PathNameOpenFilePerm() and pass default file mode for the
+ * fileMode parameter.
+ */
+File
+PathNameOpenFile(const char *fileName, int fileFlags)
+{
+	return PathNameOpenFilePerm(fileName, fileFlags, PG_FILE_MODE_DEFAULT);
+}
+
 /*
  * open a file in an arbitrary directory
  *
@@ -1300,13 +1325,13 @@ FileInvalidate(File file)
  * (which should always be $PGDATA when this code is running).
  */
 File
-PathNameOpenFile(FileName fileName, int fileFlags, int fileMode)
+PathNameOpenFilePerm(const char *fileName, int fileFlags, mode_t fileMode)
 {
 	char	   *fnamecopy;
 	File		file;
 	Vfd		   *vfdP;
 
-	DO_DB(elog(LOG, "PathNameOpenFile: %s %x %o",
+	DO_DB(elog(LOG, "PathNameOpenFilePerm: %s %x %o",
 			   fileName, fileFlags, fileMode));
 
 	/*
@@ -1324,7 +1349,7 @@ PathNameOpenFile(FileName fileName, int fileFlags, int fileMode)
 	/* Close excess kernel FDs. */
 	ReleaseLruFiles();
 
-	vfdP->fd = BasicOpenFile(fileName, fileFlags, fileMode);
+	vfdP->fd = BasicOpenFilePerm(fileName, fileFlags, fileMode);
 
 	if (vfdP->fd < 0)
 	{
@@ -1461,8 +1486,7 @@ OpenTemporaryFileInTablespace(Oid tblspcOid, bool rejectError)
 	 * temp file that can be reused.
 	 */
 	file = PathNameOpenFile(tempfilepath,
-							O_RDWR | O_CREAT | O_TRUNC | PG_BINARY,
-							0600);
+							O_RDWR | O_CREAT | O_TRUNC | PG_BINARY);
 	if (file <= 0)
 	{
 		/*
@@ -1476,8 +1500,7 @@ OpenTemporaryFileInTablespace(Oid tblspcOid, bool rejectError)
 		mkdir(tempdirpath, S_IRWXU);
 
 		file = PathNameOpenFile(tempfilepath,
-								O_RDWR | O_CREAT | O_TRUNC | PG_BINARY,
-								0600);
+								O_RDWR | O_CREAT | O_TRUNC | PG_BINARY);
 		if (file <= 0 && rejectError)
 			elog(ERROR, "could not create temporary file \"%s\": %m",
 				 tempfilepath);
@@ -2006,7 +2029,7 @@ FileGetRawFlags(File file)
 /*
  * FileGetRawMode - returns the mode bitmask passed to open(2)
  */
-int
+mode_t
 FileGetRawMode(File file)
 {
 	Assert(FileIsValid(file));
@@ -2136,12 +2159,21 @@ TryAgain:
 	return NULL;
 }
 
+/*
+ * Open a file with OpenTransientFilePerm() and pass default file mode for
+ * the fileMode parameter.
+ */
+int
+OpenTransientFile(const char *fileName, int fileFlags)
+{
+	return OpenTransientFilePerm(fileName, fileFlags, PG_FILE_MODE_DEFAULT);
+}
 
 /*
  * Like AllocateFile, but returns an unbuffered fd like open(2)
  */
 int
-OpenTransientFile(FileName fileName, int fileFlags, int fileMode)
+OpenTransientFilePerm(const char *fileName, int fileFlags, mode_t fileMode)
 {
 	int			fd;
 
@@ -2158,7 +2190,7 @@ OpenTransientFile(FileName fileName, int fileFlags, int fileMode)
 	/* Close excess kernel FDs. */
 	ReleaseLruFiles();
 
-	fd = BasicOpenFile(fileName, fileFlags, fileMode);
+	fd = BasicOpenFilePerm(fileName, fileFlags, fileMode);
 
 	if (fd >= 0)
 	{
@@ -3081,7 +3113,7 @@ pre_sync_fname(const char *fname, bool isdir, int elevel)
 	if (isdir)
 		return;
 
-	fd = OpenTransientFile((char *) fname, O_RDONLY | PG_BINARY, 0);
+	fd = OpenTransientFile(fname, O_RDONLY | PG_BINARY);
 
 	if (fd < 0)
 	{
@@ -3141,7 +3173,7 @@ fsync_fname_ext(const char *fname, bool isdir, bool ignore_perm, int elevel)
 	else
 		flags |= O_RDONLY;
 
-	fd = OpenTransientFile((char *) fname, flags, 0);
+	fd = OpenTransientFile(fname, flags);
 
 	/*
 	 * Some OSs don't allow us to open directories at all (Windows returns
diff --git a/src/backend/storage/ipc/dsm_impl.c b/src/backend/storage/ipc/dsm_impl.c
index 1500465d31..c63780139e 100644
--- a/src/backend/storage/ipc/dsm_impl.c
+++ b/src/backend/storage/ipc/dsm_impl.c
@@ -835,7 +835,7 @@ dsm_impl_mmap(dsm_op op, dsm_handle handle, Size request_size,
 
 	/* Create new segment or open an existing one for attach or resize. */
 	flags = O_RDWR | (op == DSM_OP_CREATE ? O_CREAT | O_EXCL : 0);
-	if ((fd = OpenTransientFile(name, flags, 0600)) == -1)
+	if ((fd = OpenTransientFile(name, flags)) == -1)
 	{
 		if (errno != EEXIST)
 			ereport(elevel,
diff --git a/src/backend/storage/smgr/md.c b/src/backend/storage/smgr/md.c
index 65e0abe9ec..64a4ccf0db 100644
--- a/src/backend/storage/smgr/md.c
+++ b/src/backend/storage/smgr/md.c
@@ -304,7 +304,7 @@ mdcreate(SMgrRelation reln, ForkNumber forkNum, bool isRedo)
 
 	path = relpath(reln->smgr_rnode, forkNum);
 
-	fd = PathNameOpenFile(path, O_RDWR | O_CREAT | O_EXCL | PG_BINARY, 0600);
+	fd = PathNameOpenFile(path, O_RDWR | O_CREAT | O_EXCL | PG_BINARY);
 
 	if (fd < 0)
 	{
@@ -317,7 +317,7 @@ mdcreate(SMgrRelation reln, ForkNumber forkNum, bool isRedo)
 		 * already, even if isRedo is not set.  (See also mdopen)
 		 */
 		if (isRedo || IsBootstrapProcessingMode())
-			fd = PathNameOpenFile(path, O_RDWR | PG_BINARY, 0600);
+			fd = PathNameOpenFile(path, O_RDWR | PG_BINARY);
 		if (fd < 0)
 		{
 			/* be sure to report the error reported by create, not open */
@@ -430,7 +430,7 @@ mdunlinkfork(RelFileNodeBackend rnode, ForkNumber forkNum, bool isRedo)
 		/* truncate(2) would be easier here, but Windows hasn't got it */
 		int			fd;
 
-		fd = OpenTransientFile(path, O_RDWR | PG_BINARY, 0);
+		fd = OpenTransientFile(path, O_RDWR | PG_BINARY);
 		if (fd >= 0)
 		{
 			int			save_errno;
@@ -583,7 +583,7 @@ mdopen(SMgrRelation reln, ForkNumber forknum, int behavior)
 
 	path = relpath(reln->smgr_rnode, forknum);
 
-	fd = PathNameOpenFile(path, O_RDWR | PG_BINARY, 0600);
+	fd = PathNameOpenFile(path, O_RDWR | PG_BINARY);
 
 	if (fd < 0)
 	{
@@ -594,7 +594,7 @@ mdopen(SMgrRelation reln, ForkNumber forknum, int behavior)
 		 * substitute for mdcreate() in bootstrap mode only. (See mdcreate)
 		 */
 		if (IsBootstrapProcessingMode())
-			fd = PathNameOpenFile(path, O_RDWR | O_CREAT | O_EXCL | PG_BINARY, 0600);
+			fd = PathNameOpenFile(path, O_RDWR | O_CREAT | O_EXCL | PG_BINARY);
 		if (fd < 0)
 		{
 			if ((behavior & EXTENSION_RETURN_NULL) &&
@@ -1780,7 +1780,7 @@ _mdfd_openseg(SMgrRelation reln, ForkNumber forknum, BlockNumber segno,
 	fullpath = _mdfd_segpath(reln, forknum, segno);
 
 	/* open the file */
-	fd = PathNameOpenFile(fullpath, O_RDWR | PG_BINARY | oflags, 0600);
+	fd = PathNameOpenFile(fullpath, O_RDWR | PG_BINARY | oflags);
 
 	pfree(fullpath);
 
diff --git a/src/backend/utils/cache/relmapper.c b/src/backend/utils/cache/relmapper.c
index f5394dc43d..41c2ba7f97 100644
--- a/src/backend/utils/cache/relmapper.c
+++ b/src/backend/utils/cache/relmapper.c
@@ -644,8 +644,7 @@ load_relmap_file(bool shared)
 	}
 
 	/* Read data ... */
-	fd = OpenTransientFile(mapfilename,
-						   O_RDONLY | PG_BINARY, S_IRUSR | S_IWUSR);
+	fd = OpenTransientFile(mapfilename, O_RDONLY | PG_BINARY);
 	if (fd < 0)
 		ereport(FATAL,
 				(errcode_for_file_access(),
@@ -745,9 +744,7 @@ write_relmap_file(bool shared, RelMapFile *newmap,
 		realmap = &local_map;
 	}
 
-	fd = OpenTransientFile(mapfilename,
-						   O_WRONLY | O_CREAT | PG_BINARY,
-						   S_IRUSR | S_IWUSR);
+	fd = OpenTransientFile(mapfilename, O_WRONLY | O_CREAT | PG_BINARY);
 	if (fd < 0)
 		ereport(ERROR,
 				(errcode_for_file_access(),
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index e1fd446ce5..47a5f25707 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -7242,8 +7242,7 @@ AlterSystemSetConfigFile(AlterSystemStmt *altersysstmt)
 	 * truncate and reuse it.
 	 */
 	Tmpfd = BasicOpenFile(AutoConfTmpFileName,
-						  O_CREAT | O_RDWR | O_TRUNC,
-						  S_IRUSR | S_IWUSR);
+						  O_CREAT | O_RDWR | O_TRUNC);
 	if (Tmpfd < 0)
 		ereport(ERROR,
 				(errcode_for_file_access(),
diff --git a/src/include/storage/fd.h b/src/include/storage/fd.h
index faef39e78d..6ea26e63b8 100644
--- a/src/include/storage/fd.h
+++ b/src/include/storage/fd.h
@@ -22,7 +22,7 @@
  * Use them for all file activity...
  *
  *	File fd;
- *	fd = PathNameOpenFile("foo", O_RDONLY, 0600);
+ *	fd = PathNameOpenFile("foo", O_RDONLY);
  *
  *	AllocateFile();
  *	FreeFile();
@@ -46,8 +46,6 @@
  * FileSeek uses the standard UNIX lseek(2) flags.
  */
 
-typedef char *FileName;
-
 typedef int File;
 
 
@@ -65,7 +63,8 @@ extern int	max_safe_fds;
  */
 
 /* Operations on virtual Files --- equivalent to Unix kernel file ops */
-extern File PathNameOpenFile(FileName fileName, int fileFlags, int fileMode);
+extern File PathNameOpenFile(const char *fileName, int fileFlags);
+extern File PathNameOpenFilePerm(const char *fileName, int fileFlags, mode_t fileMode);
 extern File OpenTemporaryFile(bool interXact);
 extern void FileClose(File file);
 extern int	FilePrefetch(File file, off_t offset, int amount, uint32 wait_event_info);
@@ -78,7 +77,7 @@ extern void FileWriteback(File file, off_t offset, off_t nbytes, uint32 wait_eve
 extern char *FilePathName(File file);
 extern int	FileGetRawDesc(File file);
 extern int	FileGetRawFlags(File file);
-extern int	FileGetRawMode(File file);
+extern mode_t FileGetRawMode(File file);
 
 /* Operations that allow use of regular stdio --- USE WITH CAUTION */
 extern FILE *AllocateFile(const char *name, const char *mode);
@@ -94,11 +93,13 @@ extern struct dirent *ReadDir(DIR *dir, const char *dirname);
 extern int	FreeDir(DIR *dir);
 
 /* Operations to allow use of a plain kernel FD, with automatic cleanup */
-extern int	OpenTransientFile(FileName fileName, int fileFlags, int fileMode);
+extern int	OpenTransientFile(const char *fileName, int fileFlags);
+extern int	OpenTransientFilePerm(const char *fileName, int fileFlags, mode_t fileMode);
 extern int	CloseTransientFile(int fd);
 
 /* If you've really really gotta have a plain kernel FD, use this */
-extern int	BasicOpenFile(FileName fileName, int fileFlags, int fileMode);
+extern int	BasicOpenFile(const char *fileName, int fileFlags);
+extern int	BasicOpenFilePerm(const char *fileName, int fileFlags, mode_t fileMode);
 
 /* Miscellaneous support routines */
 extern void InitFileAccess(void);