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Subject: Re: [PATCH] mm: fix page_mkclean_one
From: Mike Galbraith <efault@gmx.de>
To: Andrew Morton <akpm@osdl.org>
Cc: Linus Torvalds <torvalds@osdl.org>, Guillaume Chazarain <guichaz@yahoo.fr>,
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       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Chen Kenneth W <kenneth.w.chen@intel.com>
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Date: Thu, 28 Dec 2006 23:35:10 +0100
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On Thu, 2006-12-28 at 11:45 -0800, Andrew Morton wrote:
> On Thu, 28 Dec 2006 11:28:52 -0800 (PST)
> Linus Torvalds <torvalds@osdl.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).

I did fdatasync(), tried remapping before unmapping... nogo here.