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Date: Mon, 24 May 2010 12:32:00 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
       KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
       Nick Piggin <npiggin@suse.de>, Andrea Arcangeli <aarcange@redhat.com>,
       Avi Kivity <avi@redhat.com>, Thomas Gleixner <tglx@linutronix.de>,
       Rik van Riel <riel@redhat.com>, Ingo Molnar <mingo@elte.hu>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
       Benjamin Herrenschmidt <benh@kernel.crashing.org>,
       David Miller <davem@davemloft.net>,
       Hugh Dickins <hugh.dickins@tiscali.co.uk>, Mel Gorman <mel@csn.ul.ie>
Subject: Re: [PATCH 02/13] mm: Revalidate anon_vma in page_lock_anon_vma()
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On Fri, 09 Apr 2010 10:44:53 +0200
Peter Zijlstra <peterz@infradead.org> wrote:

> On Fri, 2010-04-09 at 16:29 +0900, KOSAKI Motohiro wrote:
> > 
> > 
> > diff --git a/mm/rmap.c b/mm/rmap.c
> > index 8b088f0..b4a0b5b 100644
> > --- a/mm/rmap.c
> > +++ b/mm/rmap.c
> > @@ -295,7 +295,7 @@ struct anon_vma *page_lock_anon_vma(struct page
> > *page)
> >         unsigned long anon_mapping;
> >  
> >         rcu_read_lock();
> > -       anon_mapping = (unsigned long) ACCESS_ONCE(page->mapping);
> > +       anon_mapping = (unsigned long) rcu_dereference(page->mapping);
> >         if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
> >                 goto out;
> >         if (!page_mapped(page)) 
> 
> Yes, I think this is indeed required.
> 
> I'll do a new version of the patch that includes the comment updates
> requested by Andrew.

Either this didn't happen or I lost the patch.

I parked mm-revalidate-anon_vma-in-page_lock_anon_vma.patch for now. 
Hopefully everything still works without it..