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Date: Mon, 25 Aug 2008 23:55:32 +0200
From: Christoph Hellwig <hch@lst.de>
Subject: Re: [2.6.27-rc4] XFS i_lock vs i_iolock...
Message-ID: <20080825215532.GB28188@lst.de>
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To: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Chinner <david@fromorbit.com>, Lachlan McIlroy <lachlan@sgi.com>, Daniel J Blueman <daniel.blueman@gmail.com>, Linux Kernel <linux-kernel@vger.kernel.org>, xfs@oss.sgi.com, hch@lst.de

On Mon, Aug 25, 2008 at 08:59:33AM +0200, Peter Zijlstra wrote:
> How can you take two locks in one go? It seems to me you always need to
> take them one after another, and as soon as you do that, you have
> ordering constraints.

Yes, you would.  Except that in all other places we only have a single
iolock involved, so the ordering of the second iolock and second ilock
don't matter.

Because of that I think declaring that xfs_lock_two_inodes can just
lock on lock type at a time might be the better solution.