linux-kernel - Re: [BUG] rmap: fix page_address_in_vma() to walk through anon_vma

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Message-ID: <20100423020632.GA7383@spritzerA.linux.bs1.fc.nec.co.jp>
Date:	Fri, 23 Apr 2010 11:06:32 +0900
From:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
To:	Rik van Riel <riel@...hat.com>
Cc:	linux-mm <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: [BUG] rmap: fix page_address_in_vma() to walk through
 anon_vma_chain

> However, for anonymous pages, page_address_in_vma only
> ever determined whether the page _could_ be part of the
> VMA, never whether it actually was.
>
> The function page_address_in_vma has always given
> false positives, which means all of the callers already
> check that the page is actually part of the process.

I see.

> This means we may be able to get away with not verifying
> the anon_vma at all.  After all, verifying that the VMA
> has the anon_vma mapped does not mean the VMA has this
> page...
> 
> Doing away with that check gets rid of your locking
> conundrum :)

I get it, thank you :)
I'll rewrite fix patch based on your comments.

Thanks,
Naoya Horiguchi
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