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 ae832917ce..5c58469425 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)
@@ -1580,8 +1580,7 @@ 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 a3e8ce092f..cfdba80fdd 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -3168,8 +3168,7 @@ 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)
@@ -3194,8 +3193,7 @@ 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(),
@@ -3291,8 +3289,7 @@ 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(),
@@ -3333,7 +3330,7 @@ XLogFileCopy(XLogSegNo destsegno, TimeLineID srcTLI, XLogSegNo srcsegno,
 	 * Open the source file
 	 */
 	XLogFilePath(path, srcTLI, srcsegno);
-	srcfd = OpenTransientFile(path, O_RDONLY | PG_BINARY, 0);
+	srcfd = OpenTransientFile(path, O_RDONLY | PG_BINARY);
 	if (srcfd < 0)
 		ereport(ERROR,
 				(errcode_for_file_access(),
@@ -3347,8 +3344,7 @@ 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(),
@@ -3526,8 +3522,7 @@ XLogFileOpen(XLogSegNo segno)
 
 	XLogFilePath(path, ThisTimeLineID, segno);
 
-	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(),
@@ -3593,7 +3588,7 @@ 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! */
@@ -4084,7 +4079,7 @@ ValidateXLOGDirectoryStructure(void)
 	{
 		ereport(LOG,
 				(errmsg("creating missing WAL directory \"%s\"", path)));
-		if (mkdir(path, S_IRWXU) < 0)
+		if (MakeDirectory(path) < 0)
 			ereport(FATAL,
 					(errmsg("could not create missing directory \"%s\": %m",
 							path)));
@@ -4428,8 +4423,7 @@ 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(),
@@ -4472,8 +4466,7 @@ 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(),
@@ -4654,8 +4647,7 @@ 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 bbae733d65..0eaba71ea8 100644
--- a/src/backend/access/transam/xlogutils.c
+++ b/src/backend/access/transam/xlogutils.c
@@ -691,7 +691,7 @@ XLogRead(char *buf, TimeLineID tli, XLogRecPtr startptr, Size count)
 
 			XLogFilePath(path, tli, sendSegNo);
 
-			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/commands/tablespace.c b/src/backend/commands/tablespace.c
index 8559c3b6b3..6350f5b459 100644
--- a/src/backend/commands/tablespace.c
+++ b/src/backend/commands/tablespace.c
@@ -151,7 +151,7 @@ TablespaceCreateDbspace(Oid spcNode, Oid dbNode, bool isRedo)
 			else
 			{
 				/* Directory creation failed? */
-				if (mkdir(dir, S_IRWXU) < 0)
+				if (MakeDirectory(dir) < 0)
 				{
 					char	   *parentdir;
 
@@ -173,7 +173,7 @@ TablespaceCreateDbspace(Oid spcNode, Oid dbNode, bool isRedo)
 					get_parent_directory(parentdir);
 					get_parent_directory(parentdir);
 					/* Can't create parent and it doesn't already exist? */
-					if (mkdir(parentdir, S_IRWXU) < 0 && errno != EEXIST)
+					if (MakeDirectory(parentdir) < 0 && errno != EEXIST)
 						ereport(ERROR,
 								(errcode_for_file_access(),
 								 errmsg("could not create directory \"%s\": %m",
@@ -184,7 +184,7 @@ TablespaceCreateDbspace(Oid spcNode, Oid dbNode, bool isRedo)
 					parentdir = pstrdup(dir);
 					get_parent_directory(parentdir);
 					/* Can't create parent and it doesn't already exist? */
-					if (mkdir(parentdir, S_IRWXU) < 0 && errno != EEXIST)
+					if (MakeDirectory(parentdir) < 0 && errno != EEXIST)
 						ereport(ERROR,
 								(errcode_for_file_access(),
 								 errmsg("could not create directory \"%s\": %m",
@@ -192,7 +192,7 @@ TablespaceCreateDbspace(Oid spcNode, Oid dbNode, bool isRedo)
 					pfree(parentdir);
 
 					/* Create database directory */
-					if (mkdir(dir, S_IRWXU) < 0)
+					if (MakeDirectory(dir) < 0)
 						ereport(ERROR,
 								(errcode_for_file_access(),
 								 errmsg("could not create directory \"%s\": %m",
@@ -279,7 +279,7 @@ CreateTableSpace(CreateTableSpaceStmt *stmt)
 	/*
 	 * Check that location isn't too long. Remember that we're going to append
 	 * 'PG_XXX/<dboid>/<relid>_<fork>.<nnn>'.  FYI, we never actually
-	 * reference the whole path here, but mkdir() uses the first two parts.
+	 * reference the whole path here, but MakeDirectory() uses the first two parts.
 	 */
 	if (strlen(location) + 1 + strlen(TABLESPACE_VERSION_DIRECTORY) + 1 +
 		OIDCHARS + 1 + OIDCHARS + 1 + FORKNAMECHARS + 1 + OIDCHARS > MAXPGPATH)
@@ -574,7 +574,7 @@ create_tablespace_directories(const char *location, const Oid tablespaceoid)
 	 * Attempt to coerce target directory to safe permissions.  If this fails,
 	 * it doesn't exist or has the wrong owner.
 	 */
-	if (chmod(location, S_IRWXU) != 0)
+	if (chmod(location, PG_DIR_MODE_DEFAULT) != 0)
 	{
 		if (errno == ENOENT)
 			ereport(ERROR,
@@ -599,7 +599,7 @@ create_tablespace_directories(const char *location, const Oid tablespaceoid)
 		if (stat(location_with_version_dir, &st) == 0 && S_ISDIR(st.st_mode))
 		{
 			if (!rmtree(location_with_version_dir, true))
-				/* If this failed, mkdir() below is going to error. */
+				/* If this failed, MakeDirectory() below is going to error. */
 				ereport(WARNING,
 						(errmsg("some useless files may be left behind in old database directory \"%s\"",
 								location_with_version_dir)));
@@ -610,7 +610,7 @@ create_tablespace_directories(const char *location, const Oid tablespaceoid)
 	 * The creation of the version directory prevents more than one tablespace
 	 * in a single location.
 	 */
-	if (mkdir(location_with_version_dir, S_IRWXU) < 0)
+	if (MakeDirectory(location_with_version_dir) < 0)
 	{
 		if (errno == EEXIST)
 			ereport(ERROR,
diff --git a/src/backend/libpq/be-fsstubs.c b/src/backend/libpq/be-fsstubs.c
index bf45461b2f..e433446922 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(),
@@ -531,16 +531,9 @@ be_lo_export(PG_FUNCTION_ARGS)
 
 	/*
 	 * open the file to be written to
-	 *
-	 * Note: we reduce backend's normal 077 umask to the slightly friendlier
-	 * 022. This code used to drop it all the way to 0, but creating
-	 * world-writable export files doesn't seem wise.
 	 */
 	text_to_cstring_buffer(filename, fnamebuf, sizeof(fnamebuf));
-	oumask = umask(S_IWGRP | S_IWOTH);
-	fd = OpenTransientFile(fnamebuf, O_CREAT | O_WRONLY | O_TRUNC | PG_BINARY,
-						   S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
-	umask(oumask);
+	fd = OpenTransientFile(fnamebuf, O_CREAT | O_WRONLY | O_TRUNC | PG_BINARY);
 	if (fd < 0)
 		ereport(ERROR,
 				(errcode_for_file_access(),
@@ -563,6 +556,18 @@ be_lo_export(PG_FUNCTION_ARGS)
 	CloseTransientFile(fd);
 	inv_close(lobj);
 
+	/*
+	 * Allow group read.  This code used make export files world-writable but that
+	 * doesn't seem wise.
+	 */
+	if (chmod(fnamebuf, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH) != 0)
+	{
+			ereport(ERROR,
+					(errcode_for_file_access(),
+					 errmsg("could not set permissions on server file \"%s\": %m",
+							fnamebuf)));
+	}
+
 	PG_RETURN_INT32(1);
 }
 
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index 95180b2ef5..11d00b854a 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -4440,7 +4440,7 @@ internal_forkexec(int argc, char *argv[], Port *port)
 		 * As in OpenTemporaryFileInTablespace, try to make the temp-file
 		 * directory
 		 */
-		mkdir(PG_TEMP_FILES_DIR, S_IRWXU);
+		MakeDirectory(PG_TEMP_FILES_DIR);
 
 		fp = AllocateFile(tmpfilename, PG_BINARY_W);
 		if (!fp)
diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c
index 3255b42c7d..f58fe8e8f1 100644
--- a/src/backend/postmaster/syslogger.c
+++ b/src/backend/postmaster/syslogger.c
@@ -41,6 +41,7 @@
 #include "postmaster/postmaster.h"
 #include "postmaster/syslogger.h"
 #include "storage/dsm.h"
+#include "storage/fd.h"
 #include "storage/ipc.h"
 #include "storage/latch.h"
 #include "storage/pg_shmem.h"
@@ -322,7 +323,7 @@ SysLoggerMain(int argc, char *argv[])
 				/*
 				 * Also, create new directory if not present; ignore errors
 				 */
-				mkdir(Log_directory, S_IRWXU);
+				MakeDirectory(Log_directory);
 			}
 			if (strcmp(Log_filename, currentLogFilename) != 0)
 			{
@@ -564,7 +565,7 @@ SysLogger_Start(void)
 	/*
 	 * Create log directory if not present; ignore errors
 	 */
-	mkdir(Log_directory, S_IRWXU);
+	MakeDirectory(Log_directory);
 
 	/*
 	 * The initial logfile is created right in the postmaster, to verify that
diff --git a/src/backend/replication/logical/origin.c b/src/backend/replication/logical/origin.c
index edc6efb8a6..edd539aa7a 100644
--- a/src/backend/replication/logical/origin.c
+++ b/src/backend/replication/logical/origin.c
@@ -547,8 +547,7 @@ CheckPointReplicationOrigin(void)
 	 * CheckpointLock.
 	 */
 	tmpfd = OpenTransientFile((char *) tmppath,
-							  O_CREAT | O_EXCL | O_WRONLY | PG_BINARY,
-							  S_IRUSR | S_IWUSR);
+							  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((char *) 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 657bafae57..98266e0613 100644
--- a/src/backend/replication/logical/reorderbuffer.c
+++ b/src/backend/replication/logical/reorderbuffer.c
@@ -2103,8 +2103,7 @@ 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,
@@ -2348,7 +2347,7 @@ 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;
@@ -3037,7 +3036,7 @@ 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 a8a16f55e9..f44e2e0d8f 100644
--- a/src/backend/replication/slot.c
+++ b/src/backend/replication/slot.c
@@ -1166,13 +1166,13 @@ CreateSlotOnDisk(ReplicationSlot *slot)
 	 * It's just barely possible that some previous effort to create or drop a
 	 * slot with this name left a temp directory lying around. If that seems
 	 * to be the case, try to remove it.  If the rmtree() fails, we'll error
-	 * out at the mkdir() below, so we don't bother checking success.
+	 * out at the MakeDirectory() below, so we don't bother checking success.
 	 */
 	if (stat(tmppath, &st) == 0 && S_ISDIR(st.st_mode))
 		rmtree(tmppath, true);
 
 	/* Create and fsync the temporary slot directory. */
-	if (mkdir(tmppath, S_IRWXU) < 0)
+	if (MakeDirectory(tmppath) < 0)
 		ereport(ERROR,
 				(errcode_for_file_access(),
 				 errmsg("could not create directory \"%s\": %m",
@@ -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 1fbe8ed71b..b3b1cc8d49 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);
 
-			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..f3d2b003aa 100644
--- a/src/backend/storage/file/copydir.c
+++ b/src/backend/storage/file/copydir.c
@@ -41,7 +41,7 @@ copydir(char *fromdir, char *todir, bool recurse)
 	char		fromfile[MAXPGPATH * 2];
 	char		tofile[MAXPGPATH * 2];
 
-	if (mkdir(todir, S_IRWXU) != 0)
+	if (MakeDirectory(todir) != 0)
 		ereport(ERROR,
 				(errcode_for_file_access(),
 				 errmsg("could not create directory \"%s\": %m", todir)));
@@ -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..e47fdceedd 100644
--- a/src/backend/storage/file/fd.c
+++ b/src/backend/storage/file/fd.c
@@ -604,7 +604,7 @@ 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((char *) newfile, PG_BINARY | O_RDWR);
 	if (fd < 0)
 	{
 		if (errno != ENOENT)
@@ -917,6 +917,16 @@ set_max_safe_fds(void)
 }
 
 /*
+ * Open a file with BasicOpenFilePerm() and pass PG_FILE_MODE_DEFAULT to the
+ * fileMode parameter.
+ */
+int
+BasicOpenFile(FileName fileName, int fileFlags)
+{
+	return BasicOpenFilePerm(fileName, fileFlags, PG_FILE_MODE_DEFAULT);
+}
+
+/*
  * BasicOpenFile --- 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,
@@ -933,7 +943,7 @@ 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(FileName fileName, int fileFlags, int fileMode)
 {
 	int			fd;
 
@@ -1084,8 +1094,8 @@ 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"));
@@ -1293,6 +1303,16 @@ FileInvalidate(File file)
 #endif
 
 /*
+ * Open a file with PathNameOpenFilePerm() and pass PG_FILE_MODE_DEFAULT to the
+ * fileMode parameter.
+ */
+File
+PathNameOpenFile(FileName fileName, int fileFlags)
+{
+	return PathNameOpenFilePerm(fileName, fileFlags, PG_FILE_MODE_DEFAULT);
+}
+
+/*
  * open a file in an arbitrary directory
  *
  * NB: if the passed pathname is relative (which it usually is),
@@ -1300,13 +1320,13 @@ FileInvalidate(File file)
  * (which should always be $PGDATA when this code is running).
  */
 File
-PathNameOpenFile(FileName fileName, int fileFlags, int fileMode)
+PathNameOpenFilePerm(FileName fileName, int fileFlags, int 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 +1344,7 @@ 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)
 	{
@@ -1461,23 +1481,21 @@ 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)
 	{
 		/*
 		 * We might need to create the tablespace's tempfile directory, if no
 		 * one has yet done so.
 		 *
-		 * Don't check for error from mkdir; it could fail if someone else
+		 * Don't check for error from MakeDirectory; it could fail if someone else
 		 * just did the same thing.  If it doesn't work then we'll bomb out on
 		 * the second create attempt, instead.
 		 */
-		mkdir(tempdirpath, S_IRWXU);
+		MakeDirectory(tempdirpath);
 
 		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);
@@ -2136,12 +2154,21 @@ TryAgain:
 	return NULL;
 }
 
+/*
+ * Open a file with OpenTransientFilePerm() and pass PG_FILE_MODE_DEFAULT to
+ * the fileMode parameter.
+ */
+int
+OpenTransientFile(FileName 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(FileName fileName, int fileFlags, int fileMode)
 {
 	int			fd;
 
@@ -2158,7 +2185,7 @@ 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 +3108,7 @@ pre_sync_fname(const char *fname, bool isdir, int elevel)
 	if (isdir)
 		return;
 
-	fd = OpenTransientFile((char *) fname, O_RDONLY | PG_BINARY, 0);
+	fd = OpenTransientFile((char *) fname, O_RDONLY | PG_BINARY);
 
 	if (fd < 0)
 	{
@@ -3141,7 +3168,7 @@ 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((char *) fname, flags);
 
 	/*
 	 * Some OSs don't allow us to open directories at all (Windows returns
@@ -3213,3 +3240,22 @@ fsync_parent_path(const char *fname, int elevel)
 
 	return 0;
 }
+
+/*
+ * Create a directory with MakeDirectoryPerm() and pass PG_DIR_MODE_DEFAULT to
+ * the directoryMode parameter.
+ */
+int
+MakeDirectory(const char *directoryName)
+{
+	return MakeDirectoryPerm(directoryName, PG_DIR_MODE_DEFAULT);
+}
+
+/*
+ * Create a directory with the specified mode.
+ */
+int
+MakeDirectoryPerm(const char *directoryName, int directoryMode)
+{
+	return mkdir(directoryName, directoryMode);
+}
diff --git a/src/backend/storage/ipc/dsm_impl.c b/src/backend/storage/ipc/dsm_impl.c
index 1500465d31..3cf34dbc4f 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 = OpenTransientFilePerm(name, flags, S_IRUSR | S_IWUSR)) == -1)
 	{
 		if (errno != EEXIST)
 			ereport(elevel,
diff --git a/src/backend/storage/ipc/ipc.c b/src/backend/storage/ipc/ipc.c
index dfb47e7c39..f3c9d9f2d3 100644
--- a/src/backend/storage/ipc/ipc.c
+++ b/src/backend/storage/ipc/ipc.c
@@ -132,8 +132,8 @@ proc_exit(int code)
 		else
 			snprintf(gprofDirName, 32, "gprof/%d", (int) getpid());
 
-		mkdir("gprof", S_IRWXU | S_IRWXG | S_IRWXO);
-		mkdir(gprofDirName, S_IRWXU | S_IRWXG | S_IRWXO);
+		MakeDirectoryPerm("gprof", S_IRWXU | S_IRWXG | S_IRWXO);
+		MakeDirectoryPerm(gprofDirName, S_IRWXU | S_IRWXG | S_IRWXO);
 		chdir(gprofDirName);
 	}
 #endif
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 bc9f09a086..e520fbace9 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -7244,8 +7244,7 @@ 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..6a7b6121e9 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();
@@ -59,13 +59,17 @@ extern int	max_files_per_process;
  */
 extern int	max_safe_fds;
 
+/* Define default file/directory modes. */
+#define PG_FILE_MODE_DEFAULT	(S_IRUSR | S_IWUSR)
+#define PG_DIR_MODE_DEFAULT		(S_IRWXU)
 
 /*
  * prototypes for functions in fd.c
  */
 
 /* Operations on virtual Files --- equivalent to Unix kernel file ops */
-extern File PathNameOpenFile(FileName fileName, int fileFlags, int fileMode);
+extern File PathNameOpenFile(FileName fileName, int fileFlags);
+extern File PathNameOpenFilePerm(FileName fileName, int fileFlags, int 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);
@@ -94,11 +98,17 @@ 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(FileName fileName, int fileFlags);
+extern int	OpenTransientFilePerm(FileName fileName, int fileFlags, int 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(FileName fileName, int fileFlags);
+extern int	BasicOpenFilePerm(FileName fileName, int fileFlags, int fileMode);
+
+/* Operations to make directories */
+extern int MakeDirectory(const char *directoryName);
+extern int MakeDirectoryPerm(const char *directoryName, int directoryMode);
 
 /* Miscellaneous support routines */
 extern void InitFileAccess(void);