linux-kernel - Re: [BUGFIX][PATCH] memcg: fix race in file

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Message-Id: <20100914133546.35d90726.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Tue, 14 Sep 2010 13:35:46 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>,
	"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>,
	gthelen@...gle.com,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	stable@...nel.org
Subject: Re: [BUGFIX][PATCH] memcg: fix race in file_mapped accouting flag
 management

On Mon, 13 Sep 2010 14:08:03 -0700
Andrew Morton <akpm@...ux-foundation.org> wrote:

> On Mon, 13 Sep 2010 16:08:22 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:
<snip>
> > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> > ---
> >  mm/memcontrol.c |    3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > Index: lockless-update/mm/memcontrol.c
> > ===================================================================
> > --- lockless-update.orig/mm/memcontrol.c
> > +++ lockless-update/mm/memcontrol.c
> > @@ -1485,7 +1485,8 @@ void mem_cgroup_update_file_mapped(struc
> >  		SetPageCgroupFileMapped(pc);
> >  	} else {
> >  		__this_cpu_dec(mem->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
> > -		ClearPageCgroupFileMapped(pc);
> > +		if (page_mapped(page)) /* for race between dec->inc counter */
> > +			ClearPageCgroupFileMapped(pc);
> >  	}
> 
> This should be !page_mapped(), shouldn't it?
> 

Ahhhh, yes. reflesh miss..

> And your second patch _does_ have !page_mapped() here, which is why the
> second patch didn't apply.
> 
Very sorry.

> I tried to fix things up.  Please check.

Thank you. 

-Kame

> 
> 
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