linux-kernel - Re: Dirty pages underflow on 3.14.23

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Message-ID: <pan.2015.01.07.10.57.46@googlemail.com>
Date:	Wed, 7 Jan 2015 10:57:46 +0000 (UTC)
From:	Holger Hoffstätte 
	<holger.hoffstaette@...glemail.com>
To:	linux-kernel@...r.kernel.org
Cc:	linux-mm@...ck.org
Subject: Re: Dirty pages underflow on 3.14.23

On Tue, 06 Jan 2015 12:54:43 -0500, Mikulas Patocka wrote:

> On Tue, 6 Jan 2015, Johannes Weiner wrote:
> 
>> > The bug probably happened during git pull or apt-get update, though
>> > one can't be sure that these commands caused it.
>> > 
>> > I see that 3.14.24 containes some fix for underflow (commit
>> > 6619741f17f541113a02c30f22a9ca22e32c9546, upstream commit
>> > abe5f972912d086c080be4bde67750630b6fb38b), but it doesn't seem that
>> > that commit fixes this condition. If you have a commit that could fix
>> > this, say it.
>> 
>> That's an unrelated counter, but there is a known dirty underflow
>> problem that was addressed in 87a7e00b206a ("mm: protect
>> set_page_dirty() from ongoing truncation").  It should make it into the
>> stable kernels in the near future.  Can you reproduce this issue?
>> 
>> Thanks,
>> Johannes
> 
> I can't reprodce it. It happened just once.
> 
> That patch is supposed to fix an occasional underflow by a single page -
> while my meminfo showed underflow by 22952KiB (5738 pages).

You are probably looking for:
commit 835f252c6debd204fcd607c79975089b1ecd3472
"aio: fix uncorrent dirty pages accouting when truncating AIO ring buffer"

It definitely went into 3.14.26, don't know about 3.16.x.

-h

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