linux-kernel - Re: [patch for-3.7 v3] mm, mempolicy: hold task->mempolicy refcount while reading numa

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Message-ID: <alpine.DEB.2.00.1210190227240.26815@chino.kir.corp.google.com>
Date:	Fri, 19 Oct 2012 02:28:42 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dave Jones <davej@...hat.com>,
	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	bhutchings@...arflare.com,
	Konstantin Khlebnikov <khlebnikov@...nvz.org>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Hugh Dickins <hughd@...gle.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [patch for-3.7 v3] mm, mempolicy: hold task->mempolicy refcount
 while reading numa_maps.

On Fri, 19 Oct 2012, Kamezawa Hiroyuki wrote:

> From c5849c9034abeec3f26bf30dadccd393b0c5c25e Mon Sep 17 00:00:00 2001
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> Date: Fri, 19 Oct 2012 17:00:55 +0900
> Subject: [PATCH] hold task->mempolicy while numa_maps scans.
> 
>  /proc/<pid>/numa_maps scans vma and show mempolicy under
>  mmap_sem. It sometimes accesses task->mempolicy which can
>  be freed without mmap_sem and numa_maps can show some
>  garbage while scanning.
> 
> This patch tries to take reference count of task->mempolicy at reading
> numa_maps before calling get_vma_policy(). By this, task->mempolicy
> will not be freed until numa_maps reaches its end.
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>

Looks good, but the patch is whitespace damaged so it doesn't apply.  When 
that's fixed:

Acked-by: David Rientjes <rientjes@...gle.com>

Thanks for following through on this!
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