Crash in virtual file descriptor FDDEBUG code

From e719e320366c9bde8608b180bcf8a42481c3a89a Mon Sep 17 00:00:00 2001
From: Greg Nancarrow <gregn4422@gmail.com>
Date: Tue, 17 Nov 2020 10:43:27 +1100
Subject: [PATCH] Fix crash in virtual file descriptor FDDEBUG code.

When virtual file descriptor FDDEBUG code is enabled, a crash occurs
within the logging code in Insert(). This results from a NULL "fileName"
being passed by PathNameOpenFilePerm(). The correction is to move the
Insert() invocation until after fileName is set in the VfdCache entry.
---
 src/backend/storage/file/fd.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/backend/storage/file/fd.c b/src/backend/storage/file/fd.c
index bd72a87..05abcf7 100644
--- a/src/backend/storage/file/fd.c
+++ b/src/backend/storage/file/fd.c
@@ -1486,8 +1486,6 @@ PathNameOpenFilePerm(const char *fileName, int fileFlags, mode_t fileMode)
 	DO_DB(elog(LOG, "PathNameOpenFile: success %d",
 			   vfdP->fd));
 
-	Insert(file);
-
 	vfdP->fileName = fnamecopy;
 	/* Saved flags are adjusted to be OK for re-opening file */
 	vfdP->fileFlags = fileFlags & ~(O_CREAT | O_TRUNC | O_EXCL);
@@ -1496,6 +1494,8 @@ PathNameOpenFilePerm(const char *fileName, int fileFlags, mode_t fileMode)
 	vfdP->fdstate = 0x0;
 	vfdP->resowner = NULL;
 
+	Insert(file);
+
 	return file;
 }
 
-- 
1.8.3.1