Date: Sat, 24 Apr 2010 13:13:40 +0200
From: Andrea Arcangeli <aarcange@redhat.com>
To: Mel Gorman <mel@csn.ul.ie>
Cc: Minchan Kim <minchan.kim@gmail.com>,
       KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
       Christoph Lameter <cl@linux-foundation.org>,
       Andrew Morton <akpm@linux-foundation.org>, Adam Litke <agl@us.ibm.com>,
       Avi Kivity <avi@redhat.com>, David Rientjes <rientjes@google.com>,
       KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
       Rik van Riel <riel@redhat.com>, linux-kernel@vger.kernel.org,
       linux-mm@kvack.org
Subject: Re: [PATCH 04/14] mm,migration: Allow the migration of
 PageSwapCache  pages
Message-ID: <20100424111340.GB32034@random.random>
References: <20100422193106.9ffad4ec.kamezawa.hiroyu@jp.fujitsu.com>
 <20100422195153.d91c1c9e.kamezawa.hiroyu@jp.fujitsu.com>
 <1271946226.2100.211.camel@barrios-desktop>
 <1271947206.2100.216.camel@barrios-desktop>
 <20100422154443.GD30306@csn.ul.ie>
 <20100423183135.GT32034@random.random>
 <20100423192311.GC14351@csn.ul.ie>
 <20100423193948.GU32034@random.random>
 <20100423213549.GV32034@random.random>
 <20100424105226.GF14351@csn.ul.ie>
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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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