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Date: Fri, 15 Feb 2013 17:24:58 +0900
From: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
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To: Michal Hocko <mhocko@suse.cz>
CC: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Johannes Weiner <hannes@cmpxchg.org>, Ying Han <yinghan@google.com>,
        Tejun Heo <htejun@gmail.com>, Glauber Costa <glommer@parallels.com>,
        Li Zefan <lizefan@huawei.com>,
        Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH v4 4/6] memcg: simplify mem_cgroup_iter
References: <1360848396-16564-1-git-send-email-mhocko@suse.cz> <1360848396-16564-5-git-send-email-mhocko@suse.cz>
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(2013/02/14 22:26), Michal Hocko wrote:
> Current implementation of mem_cgroup_iter has to consider both css and
> memcg to find out whether no group has been found (css==NULL - aka the
> loop is completed) and that no memcg is associated with the found node
> (!memcg - aka css_tryget failed because the group is no longer alive).
> This leads to awkward tweaks like tests for css && !memcg to skip the
> current node.
> 
> It will be much easier if we got rid off css variable altogether and
> only rely on memcg. In order to do that the iteration part has to skip
> dead nodes. This sounds natural to me and as a nice side effect we will
> get a simple invariant that memcg is always alive when non-NULL and all
> nodes have been visited otherwise.
> 
> We could get rid of the surrounding while loop but keep it in for now to
> make review easier. It will go away in the following patch.
> 
> Signed-off-by: Michal Hocko <mhocko@suse.cz>
nice.

Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>