From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@infradead.org>
Subject: Re: [URGENT PATCH] ext4: fix potential deadlock in ext4_evict_inode()
Date: Fri, 26 Aug 2011 04:50:57 -0400
Message-ID: <20110826085057.GA13311@infradead.org>
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Cc: Theodore Ts'o <tytso@mit.edu>, Jiaying Zhang <jiayingz@google.com>,
	linux-ext4@vger.kernel.org
To: Dave Chinner <david@fromorbit.com>
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On Fri, Aug 26, 2011 at 06:44:03PM +1000, Dave Chinner wrote:
> While the lockdep report is false positive, I agree that your
> change is the right fix to make - the IO completions are already
> queued on the workqueue, so they don't need to be flushed to get
> them to complete. All that needs to be done is call
> ext4_ioend_wait() for them to complete, and that gets rid of the
> i_mutex altogether. (*)

The really correct fix is to stop using the ioend wait like I did
in my pending series for XFS.  The only thing preventing ext4 from
doing that is that it marks pages uptodate from irq context,
before finishing the ioends.  This has a lot of nasty implications
as the the page might be marked uptodate without actually having
that state on disk.