linux-kernel - nfs accesses of FAT fs folders causes deadlock on lock

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Date:	Mon, 3 May 2010 22:59:42 -0700
From:	Fredrick Prashanth John Berchmans <fredrickprashanth@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	fredrickprashanth@...il.com
Subject: nfs accesses of FAT fs folders causes deadlock on lock_super

Hi,

A FAT fs folder was shared using nfs. Accessing it over nfs causes
deadlock on lock_super since
it is acquired by both __fat_readdir and vfat_lookup in the following
call chain.

Call chain
#lock_super <----causes deadlock
#vfat_lookup
#__lookup_hash
#lookup_one_len
#compose_entry_fh
#encode_entry
#nfs3svc_encode_entry_plus
#__fat_readdir <---does lock_super
#fat_readdir
#vfs_readdir
#nfsd_readdir
#nfsd3_proc_readdirplus
#nfsd_dispatch
#svc_process
#nfsd


Is lock_super needed in the vfat_lookup?
Can it be removed?

The box was running kernel version 2.6.27.10.
But I think the FAT code has not changed much.

Thanks,
Fredrick
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