linux-kernel - Re: [PATCH v2 4/8] memcg: convert to use cgroup_is

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Message-ID: <20130724142044.GG2540@dhcp22.suse.cz>
Date:	Wed, 24 Jul 2013 16:20:44 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Li Zefan <lizefan@...wei.com>
Cc:	Tejun Heo <tj@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Glauber Costa <glommer@...allels.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Johannes Weiner <hannes@...xchg.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Cgroups <cgroups@...r.kernel.org>, linux-mm@...ck.org
Subject: Re: [PATCH v2 4/8] memcg: convert to use cgroup_is_descendant()

On Wed 24-07-13 18:01:25, Li Zefan wrote:
> This is a preparation to kill css_id.
> 
> Signed-off-by: Li Zefan <lizefan@...wei.com>

css_is_ancestor doesn't depend on the depth of the hierarchy while
cgroup_is_descendant does. I do not think this would be an issue though
as __mem_cgroup_same_or_subtree is not called from any hot path.

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

> ---
>  mm/memcontrol.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index d12ca6f..626c426 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1434,7 +1434,7 @@ bool __mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg,
>  		return true;
>  	if (!root_memcg->use_hierarchy || !memcg)
>  		return false;
> -	return css_is_ancestor(&memcg->css, &root_memcg->css);
> +	return cgroup_is_descendant(memcg->css.cgroup, root_memcg->css.cgroup);
>  }
>  
>  static bool mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg,
> -- 
> 1.8.0.2
> 

-- 
Michal Hocko
SUSE Labs
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