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Re: [PATCH 5/6] xfs: fix buffer shudown reference count mismatch

To: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Subject: Re: [PATCH 5/6] xfs: fix buffer shudown reference count mismatch
From: Mark Tinguely <tinguely@xxxxxxx>
Date: Fri, 02 Nov 2012 12:10:02 -0500
Cc: Dave Chinner <david@xxxxxxxxxxxxx>, xfs@xxxxxxxxxxx
In-reply-to: <20121102131326.GG12578@xxxxxxxxxxxxx>
References: <1351816724-3000-1-git-send-email-david@xxxxxxxxxxxxx> <1351816724-3000-6-git-send-email-david@xxxxxxxxxxxxx> <20121102024351.GU29378@dastard> <20121102131326.GG12578@xxxxxxxxxxxxx>
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On 11/02/12 08:13, Christoph Hellwig wrote:
I don't like this.  ioend processing is very different for synchrous
writes, with the most important difference being that synchronous
writes need to wake the submitter at I/O completion.  From all I can
see your v2 patch breaks that beahviour.  For 3.7-rc I'd suggest
taking the additional reference conditionally.

For 3.8 I'm going to look into simply acquiring an additional reference
for synchronous writes during I/O submission to kill these special cases
all over the buffer code.

Testing shows that conditionally taking the additional reference does
work at avoiding the b_bhold is zero assert without causing pag is not
empty assert.


--Mark Tinguely.

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