linux-kernel - Re: [PATCH] mm: fix page_mkclean

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Date:	Thu, 28 Dec 2006 11:45:17 -0800
From:	Andrew Morton <akpm@...l.org>
To:	Linus Torvalds <torvalds@...l.org>
Cc:	Guillaume Chazarain <guichaz@...oo.fr>,
	David Miller <davem@...emloft.net>, ranma@...edrich.de,
	gordonfarquharson@...il.com, tbm@...ius.com,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>, andrei.popa@...eo.ro,
	hugh@...itas.com, nickpiggin@...oo.com.au, arjan@...radead.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Chen Kenneth W <kenneth.w.chen@...el.com>
Subject: Re: [PATCH] mm: fix page_mkclean_one

On Thu, 28 Dec 2006 11:28:52 -0800 (PST)
Linus Torvalds <torvalds@...l.org> wrote:

> 
> 
> On Thu, 28 Dec 2006, Guillaume Chazarain wrote:
> > 
> > The attached patch fixes the corruption for me.
> 
> Well, that's a good hint, but it's really just a symptom. You effectively 
> just made the test-program not even try to flush the data to disk, so the 
> page cache would stay in memory, and you'd not see the corruption as well.
> 
> So you basically disabled the code that tried to trigger the bug more 
> easily.
> 
> But the reason I say it's interesting is that "WB_SYNC_NONE" is very much 
> implicated in mm/page-writeback.c, and if there is a bug triggered by 
> WB_SYNC_NONE writebacks, then that would explain why page-writeback.c also 
> fails..
> 

It would be interesting to convert your app to do fsync() before
FADV_DONTNEED.  That would take WB_SYNC_NONE out of the picture as well
(apart from pdflush activity).

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