linux-kernel - Re: [patch] memcg: disable hierarchy support if bound to the legacy cgroup hierarchy

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Date:	Mon, 2 Mar 2015 18:58:21 +0100
From:	Michal Hocko <mhocko@...e.cz>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Vladimir Davydov <vdavydov@...allels.com>, linux-mm@...ck.org,
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [patch] memcg: disable hierarchy support if bound to the legacy
 cgroup hierarchy

On Mon 02-03-15 12:38:59, Johannes Weiner wrote:
> From: Vladimir Davydov <vdavydov@...allels.com>
> 
> If the memory cgroup controller is initially mounted in the scope of the
> default cgroup hierarchy and then remounted to a legacy hierarchy, it
> will still have hierarchy support enabled, which is incorrect. We should
> disable hierarchy support if bound to the legacy cgroup hierarchy.
> 
> Signed-off-by: Vladimir Davydov <vdavydov@...allels.com>
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>

I had this one on the radar but I wasn't sure about the first cgroup
part so I haven't acked it. Once Tejun picked it up this one is good as
well.

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

> ---
>  mm/memcontrol.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> Andrew, could you please pick this up for 4.0?  I don't think it's
> urgent enough for -stable, though.  Thanks!
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 0c86945bcc9a..68d4890fc4bd 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -5238,7 +5238,9 @@ static void mem_cgroup_bind(struct cgroup_subsys_state *root_css)
>  	 * on for the root memcg is enough.
>  	 */
>  	if (cgroup_on_dfl(root_css->cgroup))
> -		mem_cgroup_from_css(root_css)->use_hierarchy = true;
> +		root_mem_cgroup->use_hierarchy = true;
> +	else
> +		root_mem_cgroup->use_hierarchy = false;
>  }
>  
>  static u64 memory_current_read(struct cgroup_subsys_state *css,
> -- 
> 2.3.0
> 

-- 
Michal Hocko
SUSE Labs
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