linux-kernel - Re: R.I.P. pdflush

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Message-ID: <501AF0CC.6010903@suse.de>
Date:	Thu, 02 Aug 2012 17:27:40 -0400
From:	Jeff Mahoney <jeffm@...e.de>
To:	Artem Bityutskiy <artem.bityutskiy@...ux.intel.com>
Cc:	Al Viro <viro@...IV.linux.org.uk>,
	Linux Kernel Maling List <linux-kernel@...r.kernel.org>,
	Linux FS Maling List <linux-fsdevel@...r.kernel.org>
Subject: Re: R.I.P. pdflush

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On 7/25/12 11:11 AM, Artem Bityutskiy wrote:
> For example, reiserfs deadlocked quickly when I tested it using
> xfstests with resierfs quota support enabled. I spend several days
> trying to fix this, but reiserfs is quite complex and I'd say its
> locking is crazy (partially because of the BKL push-down). But I
> gave up after I realized that the dead-lock is related to the quota
> support. I disabled quotas and xfstests passed.

Thanks for mentioning this. This is due to both reiserfs_write_dquot
and reiserfs_evict_inode taking the reiserfs_write_lock. The old
reiserfs locking code depended on the recursive locking ability of the
BKL and the push-down made that a special case. This case isn't
handled so even though the write lock is supposed to be dropped to
take the journal lock safely, it's not and we end up with an ABBA case
there.

I'll work up a fix.

- -Jeff

- -- 
Jeff Mahoney
SUSE Labs
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