linux-kernel - Re: [PATCH] memcg: fix Bad page state after replace_page

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Date:	Thu, 19 Apr 2012 12:20:32 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Hugh Dickins <hughd@...gle.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Miklos Szeredi <mszeredi@...e.cz>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Johannes Weiner <hannes@...xchg.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] memcg: fix Bad page state after replace_page_cache

On Wed 18-04-12 23:34:46, Hugh Dickins wrote:
> My 9ce70c0240d0 "memcg: fix deadlock by inverting lrucare nesting" put a
> nasty little bug into v3.3's version of mem_cgroup_replace_page_cache(),
> sometimes used for FUSE.  Replacing __mem_cgroup_commit_charge_lrucare()
> by __mem_cgroup_commit_charge(), I used the "pc" pointer set up earlier:
> but it's for oldpage, and needs now to be for newpage.  Once oldpage was
> freed, its PageCgroupUsed bit (cleared above but set again here) caused
> "Bad page state" messages - and perhaps worse, being missed from newpage.
> (I didn't find this by using FUSE, but in reusing the function for tmpfs.)
> 
> Signed-off-by: Hugh Dickins <hughd@...gle.com>

Acked-by: Michal Hocko <mhocko@...e.cz>

Thanks

> Cc: stable@...r.kernel.org [v3.3 only]
> ---
> 
>  mm/memcontrol.c |    1 +
>  1 file changed, 1 insertion(+)
> 
> --- 3.4-rc3/mm/memcontrol.c	2012-04-15 20:47:37.151777506 -0700
> +++ linux/mm/memcontrol.c	2012-04-18 22:29:18.490639511 -0700
> @@ -3392,6 +3392,7 @@ void mem_cgroup_replace_page_cache(struc
>  	 * the newpage may be on LRU(or pagevec for LRU) already. We lock
>  	 * LRU while we overwrite pc->mem_cgroup.
>  	 */
> +	pc = lookup_page_cgroup(newpage);
>  	__mem_cgroup_commit_charge(memcg, newpage, 1, pc, type, true);
>  }
>  
> 
> --
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-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic
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