linux-kernel - Re: [PATCH 02/13] mm: Revalidate anon_vma in page_lock_anon

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Message-ID: <1270802693.20295.3272.camel@laptop>
Date:	Fri, 09 Apr 2010 10:44:53 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Nick Piggin <npiggin@...e.de>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Avi Kivity <avi@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Rik van Riel <riel@...hat.com>, Ingo Molnar <mingo@...e.hu>,
	akpm@...ux-foundation.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	David Miller <davem@...emloft.net>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	Mel Gorman <mel@....ul.ie>
Subject: Re: [PATCH 02/13] mm: Revalidate anon_vma in page_lock_anon_vma()

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.

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