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Date: Mon, 15 Mar 2010 14:06:20 +0900
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
To: Mel Gorman <mel@csn.ul.ie>
Cc: Andrew Morton <akpm@linux-foundation.org>,
       Andrea Arcangeli <aarcange@redhat.com>,
       Christoph Lameter <cl@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 01/11] mm,migration: Take a reference to the anon_vma
 before migrating
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On Fri, 12 Mar 2010 16:41:17 +0000
Mel Gorman <mel@csn.ul.ie> wrote:

> rmap_walk_anon() does not use page_lock_anon_vma() for looking up and
> locking an anon_vma and it does not appear to have sufficient locking to
> ensure the anon_vma does not disappear from under it.
> 
> This patch copies an approach used by KSM to take a reference on the
> anon_vma while pages are being migrated. This should prevent rmap_walk()
> running into nasty surprises later because anon_vma has been freed.
> 
> Signed-off-by: Mel Gorman <mel@csn.ul.ie>
> Acked-by: Rik van Riel <riel@redhat.com>
> ---
>  include/linux/rmap.h |   23 +++++++++++++++++++++++
>  mm/migrate.c         |   12 ++++++++++++
>  mm/rmap.c            |   10 +++++-----
>  3 files changed, 40 insertions(+), 5 deletions(-)
> 
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>