linux-kernel - Re: [BUGFIX][PATCH v4] memcg: fix memory migration of shmem swapcache

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Message-ID: <20110110090503.GD2613@balbir.in.ibm.com>
Date:	Mon, 10 Jan 2011 14:35:03 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	Daisuke Nishimura <nishimura@....nes.nec.co.jp>
Cc:	Minchan Kim <minchan.kim@...il.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>
Subject: Re: [BUGFIX][PATCH v4] memcg: fix memory migration of shmem
 swapcache

* nishimura@....nes.nec.co.jp <nishimura@....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@....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>
> Reviewed-by: Minchan Kim <minchan.kim@...il.com>
> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>


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