linux-kernel - Re: [PATCH] memcg: fix mapcount check in move charge code for anonymous page

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Message-Id: <20120308144855.271ed829.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Thu, 8 Mar 2012 14:48:55 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc:	linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	Hillf Danton <dhillf@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] memcg: fix mapcount check in move charge code for
 anonymous page

On Fri,  2 Mar 2012 15:35:08 -0500
Naoya Horiguchi <n-horiguchi@...jp.nec.com> wrote:

> Currently charge on shared anonyous pages is supposed not to moved
> in task migration. To implement this, we need to check that mapcount > 1,
> instread of > 2. So this patch fixes it.
> 
> Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>

Hm. I don't remember why this check uses mapcount > 2...maybe bug.

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


> ---
>  mm/memcontrol.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git linux-next-20120228.orig/mm/memcontrol.c linux-next-20120228/mm/memcontrol.c
> index b6d1bab..785f6d3 100644
> --- linux-next-20120228.orig/mm/memcontrol.c
> +++ linux-next-20120228/mm/memcontrol.c
> @@ -5102,7 +5102,7 @@ static struct page *mc_handle_present_pte(struct vm_area_struct *vma,
>  		return NULL;
>  	if (PageAnon(page)) {
>  		/* we don't move shared anon */
> -		if (!move_anon() || page_mapcount(page) > 2)
> +		if (!move_anon() || page_mapcount(page) > 1)
>  			return NULL;
>  	} else if (!move_file())
>  		/* we ignore mapcount for file pages */
> -- 
> 1.7.7.6
> 
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