Don't Insert() a VFD entry until it's fully built.

Otherwise, if FDDEBUG is enabled, the debugging output fails because
it tries to read the fileName, which isn't set up yet (and should in
fact always be NULL).

AFAICT, this has been wrong since Berkeley.  Before 96bf88d52,
it would accidentally fail to crash on platforms where snprintf()
is forgiving about being passed a NULL pointer for %s; but the
file name intended to be included in the debug output wouldn't
ever have shown up.

Report and fix by Greg Nancarrow.  Although this is only visibly
broken in custom-made builds, it still seems worth back-patching
to all supported branches, as the FDDEBUG code is pretty useless
as it stands.

Discussion: https://postgr.es/m/CAJcOf-cUDgm9qYtC_B6XrC6MktMPNRby2p61EtSGZKnfotMArw@mail.gmail.com

diff --git a/src/backend/storage/file/fd.c b/src/backend/storage/file/fd.c
index 9004fe43cdedcd022277c28125f9dfb4d1fc476b..ae3078bcc514e80ad531d45d32d29710e6716529 100644 (file)
--- a/src/backend/storage/file/fd.c
+++ b/src/backend/storage/file/fd.c
@@ -1360,8 +1360,6 @@ PathNameOpenFile(FileName fileName, int fileFlags, int 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);
@@ -1371,6 +1369,8 @@ PathNameOpenFile(FileName fileName, int fileFlags, int fileMode)
    vfdP->fdstate = 0x0;
    vfdP->resowner = NULL;
 
+   Insert(file);
+
    return file;
 }