linux-kernel - Re: [PATCH 3/4] memcg: clear pc->mem

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Date:	Tue, 20 Dec 2011 09:35:24 +0900
From:	Hiroyuki Kamezawa <kamezawa.hiroyuki@...il.com>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Michal Hocko <mhocko@...e.cz>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>, Ying Han <yinghan@...gle.com>
Subject: Re: [PATCH 3/4] memcg: clear pc->mem_cgorup if necessary.

2011/12/20 Johannes Weiner <hannes@...xchg.org>:
> On Wed, Dec 14, 2011 at 04:51:24PM +0900, KAMEZAWA Hiroyuki wrote:
>> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
>>
>> This is a preparation before removing a flag PCG_ACCT_LRU in page_cgroup
>> and reducing atomic ops/complexity in memcg LRU handling.
>>
>> In some cases, pages are added to lru before charge to memcg and pages
>> are not classfied to memory cgroup at lru addtion. Now, the lru where
>> the page should be added is determined a bit in page_cgroup->flags and
>> pc->mem_cgroup. I'd like to remove the check of flag.
>>
>> To handle the case pc->mem_cgroup may contain stale pointers if pages are
>> added to LRU before classification. This patch resets pc->mem_cgroup to
>> root_mem_cgroup before lru additions.
>>
>> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
>
> The followup compilation fixes aside, I agree.  But the sites where
> the owner is actually reset are really not too obvious.  How about the
> comment patch below?
>
> Otherwise,
>
> Acked-by: Johannes Weiner <hannes@...xchg.org>
>
> ---
> From: Johannes Weiner <hannes@...xchg.org>
> Subject: memcg: clear pc->mem_cgorup if necessary fix
>
> Add comments to the clearing sites.
>
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>

Ah, yes. This seems better. Thank you.
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
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