linux-kernel - Re: [rfc][patch] mm: dirty page accounting race fix

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Message-ID: <48A494B0.3050509@goop.org>
Date:	Thu, 14 Aug 2008 13:25:20 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Hugh Dickins <hugh@...itas.com>
CC:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Nick Piggin <npiggin@...e.de>,
	Linux Memory Management List <linux-mm@...ck.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [rfc][patch] mm: dirty page accounting race fix

Hugh Dickins wrote:
> I realized that was the intended optimization, what I'd missed is that
> dirty_accountable can only be true there if (vma->vm_flags & VM_WRITE):
> that's checked in vma_wants_writenotify(), which is how dirty_accountable
> gets to be set.
>
> So those lines are okay, panic over, phew.
>   

I got bitten by precisely the same train of thought.  I think that code 
officially Non Obvious (or at least Not Immediately Obvious, which is 
bad in security-sensitive code).

    J
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