linux-ext4 - Re: [URGENT PATCH] ext4: fix potential deadlock in ext4_evict

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Message-ID: <4E57630B.7000202@tao.ma>
Date:	Fri, 26 Aug 2011 17:10:35 +0800
From:	Tao Ma <tm@....ma>
To:	Christoph Hellwig <hch@...radead.org>
CC:	Dave Chinner <david@...morbit.com>, Theodore Ts'o <tytso@....edu>,
	Jiaying Zhang <jiayingz@...gle.com>, linux-ext4@...r.kernel.org
Subject: Re: [URGENT PATCH] ext4: fix potential deadlock in ext4_evict_inode()

Hi Christoph,
On 08/26/2011 04:50 PM, Christoph Hellwig wrote:
> 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.
yeah, the DIO read on a buffer write file issue is also another side
effect of it.[1]
So could you please talk a little more about how xfs handle it now?

[1] http://www.spinics.net/lists/linux-ext4/msg27139.html

Thanks
Tao
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