linux-kernel - Re: [PATCH -v2] memcg: don't do cleanup manually if mem_cgroup_css

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Message-ID: <20130403085056.GD14384@dhcp22.suse.cz>
Date:	Wed, 3 Apr 2013 10:50:56 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Li Zefan <lizefan@...wei.com>
Cc:	Glauber Costa <glommer@...allels.com>,
	Johannes Weiner <hannes@...xchg.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Cgroups <cgroups@...r.kernel.org>, linux-mm@...ck.org
Subject: Re: [PATCH -v2] memcg: don't do cleanup manually if
 mem_cgroup_css_online() fails

On Wed 03-04-13 16:37:53, Li Zefan wrote:
> >>> But memcg_update_cache_sizes calls memcg_kmem_clear_activated on the
> >>> error path.
> >>>
> >>
> >> But memcg_kmem_mark_dead() checks the ACCOUNT flag not the ACCOUNTED flag.
> >> Am I missing something?
> >>
> > 
> > Dang. You are right! Glauber, is there any reason why
> > memcg_kmem_mark_dead checks only KMEM_ACCOUNTED_ACTIVE rather than
> > KMEM_ACCOUNTED_MASK?
> > 
> > This all is very confusing to say the least.
> > 
> > Anyway, this all means that Li's first patch is correct. I am not sure I
> > like it though. I think that the refcount cleanup should be done as
> > close to where it has been taken as possible otherwise we will end up in
> > this "chase the nasty details" again and again. There are definitely two
> > bugs here. The one introduced by e4715f01 and the other one introduced
> > even earlier (I haven't checked that history yet). I think we should do
> > something like the 2 follow up patches but if you guys think that the smaller
> > patch from Li is more appropriate then I will not block it.
> > 
> 
> Or we can queue my patch for 3.9, and then see if we want to change the
> tear down process, and if yes we make the change for 3.10.

OK, I thought it would be easier but I always end up with something
similar to your patch. So feel free to add my Acked-by and parts of my
changelog that fit (namely obvious bug introduced by e4715f01 and
documentnation of the clean-up path). I have a split up version in case
others like it more - will follow.

Thanks!
-- 
Michal Hocko
SUSE Labs
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