linux-kernel - Re: [PATCH 04/14] mm,migration: Allow the migration of PageSwapCache pages

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Date:	Sat, 24 Apr 2010 13:13:40 +0200
From:	Andrea Arcangeli <aarcange@...hat.com>
To:	Mel Gorman <mel@....ul.ie>
Cc:	Minchan Kim <minchan.kim@...il.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Adam Litke <agl@...ibm.com>, Avi Kivity <avi@...hat.com>,
	David Rientjes <rientjes@...gle.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Rik van Riel <riel@...hat.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [PATCH 04/14] mm,migration: Allow the migration of
 PageSwapCache  pages

On Sat, Apr 24, 2010 at 11:52:27AM +0100, Mel Gorman wrote:
> I think you're right. This is a new bug introduced by the anon_vma changes. On
> the plus side, it means we don't have to worry about -stable.

Correct, no worry about -stable.

> > vma_adjust already takes the anon_vma->lock and of course I also
> > further verified that trying to apply your snippet to vma_adjust
> > results in immediately deadlock as the very same lock is already taken
> > in my tree as it's the same anon-vma (simpler).
> 
> Yes, I expected that. Previously, there was only one anon_vma so if you
> double-take the lock, bad things happen.
> 
> > So aa.git will be
> > immune from these bugs for now.
> > 
> 
> It should be. I expect that's why you have never seen the bugon in
> swapops.

Correct, I never seen it, and I keep it under very great stress with
swap storms of hugepages, lots of I/O and khugepaged at 100% cpu.

Also keep in mind expand_downwards which also adjusts
vm_start/vm_pgoff the same way (and without mmap_sem write mode).
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