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Date: Tue, 2 Aug 2016 14:42:32 +0200
From: Michal Hocko <mhocko@kernel.org>
To: Vladimir Davydov <vdavydov@virtuozzo.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        Johannes Weiner <hannes@cmpxchg.org>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/3] mm: memcontrol: fix swap counter leak on swapout
 from offline cgroup
Message-ID: <20160802124231.GJ12403@dhcp22.suse.cz>
References: <01cbe4d1a9fd9bbd42c95e91694d8ed9c9fc2208.1470057819.git.vdavydov@virtuozzo.com>
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On Mon 01-08-16 16:26:24, Vladimir Davydov wrote:
[...]
> +static struct mem_cgroup *mem_cgroup_id_get_active(struct mem_cgroup *memcg)
> +{
> +	while (!atomic_inc_not_zero(&memcg->id.ref))
> +		memcg = parent_mem_cgroup(memcg);
> +	return memcg;
> +}

Does this actually work properly? Say we have root -> A so parent is
NULL if root (use_hierarchy == false).
-- 
Michal Hocko
SUSE Labs