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Date: Mon, 10 Jan 2011 14:35:03 +0530
From: Balbir Singh <balbir@linux.vnet.ibm.com>
To: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Minchan Kim <minchan.kim@gmail.com>, Johannes Weiner <hannes@cmpxchg.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
        LKML <linux-kernel@vger.kernel.org>, linux-mm <linux-mm@kvack.org>
Subject: Re: [BUGFIX][PATCH v4] memcg: fix memory migration of shmem
 swapcache
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* nishimura@mxp.nes.nec.co.jp <nishimura@mxp.nes.nec.co.jp> [2011-01-06 15:29:11]:

> > Sorry for nit-picking but succeed is not as good as succeeded,
> > successful, successful_migration or migration_ok
> > 
> OK, I use "migration_ok".
> 
> ===
> From: Daisuke Nishimura <nishimura@mxp.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@mxp.nes.nec.co.jp>
> Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>


Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
 
-- 
	Three Cheers,
	Balbir