linux-kernel - Re: [PATCH 5/6] mempolicy: fix a memory corruption by refcount imbalance in alloc_pages

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Message-ID: <CAHGf_=omc4g_JHu+mr-HKmoH=juhcXKgPGOKamAOrJCWkbdEMQ@mail.gmail.com>
Date:	Tue, 12 Jun 2012 12:31:29 -0400
From:	KOSAKI Motohiro <kosaki.motohiro@...il.com>
To:	Mel Gorman <mgorman@...e.de>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Andrew Morton <akpm@...gle.com>, Dave Jones <davej@...hat.com>,
	Christoph Lameter <cl@...ux.com>, stable@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Miao Xie <miaox@...fujitsu.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH 5/6] mempolicy: fix a memory corruption by refcount
 imbalance in alloc_pages_vma()

> Why does dequeue_huge_page_vma() not need to be changed as well? It's
> currently using mpol_cond_put() but if there is a goto retry_cpuset then
> will it have not take an additional reference count and leak?

dequeue_huge_page_vma() also uses get_vma_policy() and mpol_cond_put()
pair. thus we don't need special concern.


> Would it be more straight forward to put the mpol_cond_put() and __mpol_put()
> calls after the "goto retry_cpuset" checks instead?

I hope to keep symmetric. Sane design prevent a lot of unintentional breakage.
Frankly says, now all caller assume the symmetric. It's natural.
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