linux-kernel - Re: [BUGFIX][PATCH] memcg: fix memory migration of shmem swapcache

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Message-Id: <20110106105539.e55026d4.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Thu, 6 Jan 2011 10:55:39 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Daisuke Nishimura <nishimura@....nes.nec.co.jp>
Cc:	Johannes Weiner <hannes@...xchg.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>
Subject: Re: [BUGFIX][PATCH] memcg: fix memory migration of shmem swapcache

On Thu, 6 Jan 2011 10:09:23 +0900
Daisuke Nishimura <nishimura@....nes.nec.co.jp> wrote:

> ===
> From: Daisuke Nishimura <nishimura@....nes.nec.co.jp>
> 
> In current implimentation, mem_cgroup_end_migration() decides whether the page
> migration has succeeded or not by checking "oldpage->mapping".
> 
> But if we are tring to migrate a shmem swapcache, the page->mapping of it is
> NULL from the begining, so the check would be invalid.
> As a result, mem_cgroup_end_migration() assumes the migration has succeeded
> even if it's not, so "newpage" would be freed while it's not uncharged.
> 
> This patch fixes it by passing mem_cgroup_end_migration() the result of the
> page migration.
> 
> Signed-off-by: Daisuke Nishimura <nishimura@....nes.nec.co.jp>

Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>

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