pg_internal.init and an index file have the same inode

I'm not sure if this is an XFS problem, or Postgres. There's enough
suspicious evidence that it's too hard to say.

Today, I get an interesting issue raised whereby a reasonably simple
query fails on a system that does take successful pg_dumps regularly.
To make a short story shorter, I end up with the following situation
on an index relation file:

$ sha1sum 16587.8 pg_internal.init
4a0f94285c182b67175d6a68669c6b9fd46fa11e 16587.8
4a0f94285c182b67175d6a68669c6b9fd46fa11e pg_internal.init

And, even more interestingly,

$ stat 16587.8 pg_internal.init
File: `16587.8'
Size: 98532 Blocks: 200 IO Block: 4096 regular file
Device: fe00h/65024d Inode: 1073741952 Links: 1
Access: (0600/-rw-------) Uid: ( 107/postgres) Gid: ( 115/postgres)
Access: 2011-12-14 23:35:35.630043643 +0000
Modify: 2011-12-14 23:35:35.630043643 +0000
Change: 2011-12-14 23:35:35.630043643 +0000
File: `pg_internal.init'
Size: 98532 Blocks: 200 IO Block: 4096 regular file
Device: fe00h/65024d Inode: 1073741952 Links: 1
Access: (0600/-rw-------) Uid: ( 107/postgres) Gid: ( 115/postgres)
Access: 2011-12-14 23:35:35.630043643 +0000
Modify: 2011-12-14 23:35:35.630043643 +0000
Change: 2011-12-14 23:35:35.630043643 +0000

Most notably, the inode numbers are the same. At first, I thought
this was a file descriptor race in PG, but then I noticed the file
system only reports *one* link: that doesn't look like a valid state
for XFS. Should I raise this on their mailing list, and would
pgsql-hackers like to know more about this? Also, consider this an
advisory, as this was found on a vanilla Ubuntu Lucid 10.04 machine.

As such, I do think this probably could have happened to a non-index
relation file.

This database has had uptime since mid-December, and that inode seems
to have been modified at the time of the last reboot. The database
was born in October via point-in-time recovery.

...Happy New Year!

--
fdr