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* Empty core dumps on NFSv4 mounts
@ 2010-07-02  8:01 Arnaud Giersch
  2010-07-02 13:03 ` Trond Myklebust
  0 siblings, 1 reply; 5+ messages in thread
From: Arnaud Giersch @ 2010-07-02  8:01 UTC (permalink / raw)
  To: linux-nfs

Hi,

On NFSv4 mounts, many core dumps are empty, although ulimit -c is
unlimited.  An ls command shortly after the core dump often shows
4294967294 (2^32-2) as UID and GID for the "core" file.

This only happens when there was no "core" file before the dump.  If a
"core" file owned by the current user is already present, it is
correctly filled.

After having done a git bisect, it seems that the problem was
introduced by commit 80e52aced138bb41b045a8595a87510f27d8d8c5
(NFSv4: Don't do idmapper upcalls for asynchronous RPC calls).

If I understand correctly what happens, do_coredump() [fs/exec.c] fails
because (inode->i_uid != current_fsuid()).  In fact inode->i_uid equals
-2, because decode_attr_owner() [fs/nfs/nfs4xdr.c], which is called from
nfs4_xdr_dec_open() via decode_getfattr(), returns without calling
nfs_map_to_uid(), since its may_sleep parameter is false.

I however do not clearly understand what the aforementioned commit is
supposed to fix.  I read the linux-nfs mailing list archive, and tried
some google search, but I didn't find anything.

Regards,

        Arnaud Giersch

^ permalink raw reply	[flat|nested] 5+ messages in thread

end of thread, other threads:[~2010-09-21 11:25 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2010-07-02  8:01 Empty core dumps on NFSv4 mounts Arnaud Giersch
2010-07-02 13:03 ` Trond Myklebust
2010-07-05 13:28   ` [PATCH/RFC 2.6.35-rc4] NFSv4: Don't do idmapper upcalls during XDR decode Arnaud Giersch
2010-08-12 10:15     ` [PATCH 2.6.35] " Arnaud Giersch
2010-09-21 11:17       ` [PATCH resend] " Arnaud Giersch

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