linux-kernel - Re: Dirty pages underflow on 3.14.23

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Message-ID: <alpine.LRH.2.02.1501061246400.16437@file01.intranet.prod.int.rdu2.redhat.com>
Date:	Tue, 6 Jan 2015 12:54:43 -0500 (EST)
From:	Mikulas Patocka <mpatocka@...hat.com>
To:	Johannes Weiner <hannes@...xchg.org>
cc:	Vlastimil Babka <vbabka@...e.cz>, Leon Romanovsky <leon@...n.nu>,
	Mel Gorman <mgorman@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: Dirty pages underflow on 3.14.23



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).

Mikulas
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