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Re: [PATCH] xfs: Fix WARN_ON(delalloc) in xfs_vm_releasepage()

To: Jan Kara <jack@xxxxxxx>
Subject: Re: [PATCH] xfs: Fix WARN_ON(delalloc) in xfs_vm_releasepage()
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Sat, 16 Mar 2013 18:35:08 +1100
Cc: xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1363267854-25602-1-git-send-email-jack@xxxxxxx>
References: <1363267854-25602-1-git-send-email-jack@xxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Thu, Mar 14, 2013 at 02:30:54PM +0100, Jan Kara wrote:
> When a dirty page is truncated from a file but reclaim gets to it before
> truncate_inode_pages(), we hit WARN_ON(delalloc) in
> xfs_vm_releasepage(). This is because reclaim tries to write the page,
> xfs_vm_writepage() just bails out (leaving page clean) and thus reclaim
> thinks it can continue and calls xfs_vm_releasepage() on page with dirty
> buffers.
> 
> Fix the issue by redirtying the page in xfs_vm_writepage(). This makes
> reclaim stop reclaiming the page and also logically it keeps page in a
> more consistent state where page with dirty buffers has PageDirty set.
> 
> Signed-off-by: Jan Kara <jack@xxxxxxx>

Definitely look s like a problem taht needs fixing, and it seems to
me to be the correct fix.

I got a bug report recently about this warning being triggered,
but the total report was the warning and a workload description
of "XFS produced a warning at some point during a 28 hour long DB
benchmark." Not particularly helpful, but this looks like a
potential cause. Thanks!

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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