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From: Jeremy Fitzhardinge <jeremy@goop.org>
To: Hugh Dickins <hugh@veritas.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Nick Piggin <npiggin@suse.de>,
	Linux Memory Management List <linux-mm@kvack.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [rfc][patch] mm: dirty page accounting race fix
Date: Thu, 14 Aug 2008 13:25:20 -0700	[thread overview]
Message-ID: <48A494B0.3050509@goop.org> (raw)
In-Reply-To: <Pine.LNX.4.64.0808141328090.11013@blonde.site>

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

WARNING: multiple messages have this Message-ID (diff)
From: Jeremy Fitzhardinge <jeremy@goop.org>
To: Hugh Dickins <hugh@veritas.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Nick Piggin <npiggin@suse.de>,
	Linux Memory Management List <linux-mm@kvack.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [rfc][patch] mm: dirty page accounting race fix
Date: Thu, 14 Aug 2008 13:25:20 -0700	[thread overview]
Message-ID: <48A494B0.3050509@goop.org> (raw)
In-Reply-To: <Pine.LNX.4.64.0808141328090.11013@blonde.site>

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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  reply	other threads:[~2008-08-14 20:26 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-08-14  9:45 [rfc][patch] mm: dirty page accounting race fix Nick Piggin
2008-08-14  9:45 ` Nick Piggin
2008-08-14 10:27 ` Peter Zijlstra
2008-08-14 10:27   ` Peter Zijlstra
2008-08-14 11:55 ` Hugh Dickins
2008-08-14 11:55   ` Hugh Dickins
2008-08-14 12:18   ` Peter Zijlstra
2008-08-14 12:18     ` Peter Zijlstra
2008-08-14 12:47     ` Hugh Dickins
2008-08-14 12:47       ` Hugh Dickins
2008-08-14 20:25       ` Jeremy Fitzhardinge [this message]
2008-08-14 20:25         ` Jeremy Fitzhardinge
2008-08-14 12:35   ` Nick Piggin
2008-08-14 12:35     ` Nick Piggin
2008-08-14 13:20     ` Hugh Dickins
2008-08-14 13:20       ` Hugh Dickins
2008-08-14 12:49   ` Peter Zijlstra
2008-08-14 12:49     ` Peter Zijlstra
2008-08-14 13:39     ` Hugh Dickins
2008-08-14 13:39       ` Hugh Dickins
2008-08-14 13:52       ` Nick Piggin
2008-08-14 13:52         ` Nick Piggin
2008-08-14 19:09         ` Hugh Dickins
2008-08-14 19:09           ` Hugh Dickins

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