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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: Rik van Riel <riel@redhat.com>
Subject: Re: [PATCH 04/09] memcg: make zone_reclaim_stat
Cc: kosaki.motohiro@jp.fujitsu.com, LKML <linux-kernel@vger.kernel.org>,
       linux-mm <linux-mm@kvack.org>,
       Andrew Morton <akpm@linux-foundation.org>,
       Balbir Singh <balbir@linux.vnet.ibm.com>,
       KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
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References: <20081130195731.8151.KOSAKI.MOTOHIRO@jp.fujitsu.com> <4932BA80.3060708@redhat.com>
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Date: Mon,  1 Dec 2008 09:50:05 +0900 (JST)
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> KOSAKI Motohiro wrote:
> 
> > @@ -172,6 +173,10 @@ void activate_page(struct page *page)
> >  
> >  		reclaim_stat->recent_rotated[!!file]++;
> >  		reclaim_stat->recent_scanned[!!file]++;
> > +
> > +		memcg_reclaim_stat = mem_cgroup_get_reclaim_stat_by_page(page);
> > +		memcg_reclaim_stat->recent_rotated[!!file]++;
> > +		memcg_reclaim_stat->recent_scanned[!!file]++;
> 
> Also, manipulation of the zone based reclaim_stats happens
> under the lru lock.
> 
> What protects the memcg reclaim stat?

memcg zone and memcg zone_reclaim_stat also use zone->lru_lock.