From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1757213Ab0DIIpA (ORCPT <rfc822;w@1wt.eu>);
	Fri, 9 Apr 2010 04:45:00 -0400
Received: from casper.infradead.org ([85.118.1.10]:46609 "EHLO
	casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1754913Ab0DIIo6 (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Fri, 9 Apr 2010 04:44:58 -0400
Subject: Re: [PATCH 02/13] mm: Revalidate anon_vma in page_lock_anon_vma()
From: Peter Zijlstra <peterz@infradead.org>
To: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: 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>,
       akpm@linux-foundation.org,
       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>
In-Reply-To: <20100409160252.80E6.A69D9226@jp.fujitsu.com>
References: <20100409150335.80E3.A69D9226@jp.fujitsu.com>
	 <20100409154730.e9945cbc.kamezawa.hiroyu@jp.fujitsu.com>
	 <20100409160252.80E6.A69D9226@jp.fujitsu.com>
Content-Type: text/plain; charset="UTF-8"
Date: Fri, 09 Apr 2010 10:44:53 +0200
Message-ID: <1270802693.20295.3272.camel@laptop>
Mime-Version: 1.0
X-Mailer: Evolution 2.28.3 
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

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.