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Re: [PATCH 2/2] xfs: fix splice/direct-IO deadlock

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: [PATCH 2/2] xfs: fix splice/direct-IO deadlock
From: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Date: Wed, 28 Nov 2012 11:07:36 -0500
Cc: linux-fsdevel@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx
In-reply-to: <1354068768-4316-3-git-send-email-david@xxxxxxxxxxxxx>
References: <1354068768-4316-1-git-send-email-david@xxxxxxxxxxxxx> <1354068768-4316-3-git-send-email-david@xxxxxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Wed, Nov 28, 2012 at 01:12:48PM +1100, Dave Chinner wrote:
> From: Dave Chinner <dchinner@xxxxxxxxxx>
> lockdep reports splice vs direct-io write lock inversions due to
> generic_file_splice_write() taking the inode->i_mutex inside
> XFS_IOLOCK_EXCL context. These lock contexts are inverted, hence can
> deadlock.  Remove the XFS_IOLOCK_EXCL locking context from the outer
> function and drive it inwards to the actor function that only locks
> the inode when the lock is really needed,


Otherwise the patch looks fine, but I'd love to understand why the
generic code thes te I_MUTEX_CHILD annotation and we can get away
without it.

Also can you add a testcase for this to xfstests?

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