Re: [PATCH 3/4] memcg: clear pc->mem_cgorup if necessary.

Hiroyuki Kamezawa
2011-12-20T00:35:27Z

2011/12/20 Johannes Weiner <hannes@cmpxchg.org>:
> On Wed, Dec 14, 2011 at 04:51:24PM +0900, KAMEZAWA Hiroyuki wrote:
>> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.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@jp.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@cmpxchg.org>
>
> ---
> From: Johannes Weiner <hannes@cmpxchg.org>
> Subject: memcg: clear pc->mem_cgorup if necessary fix
>
> Add comments to the clearing sites.
>
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>

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