linux-kernel - Re: [PATCH 1/3] mm: memcontrol: fix swap counter leak on swapout from offline cgroup

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Message-ID: <20160802132200.GE13263@esperanza>
Date:	Tue, 2 Aug 2016 16:22:00 +0300
From:	Vladimir Davydov <vdavydov@...tuozzo.com>
To:	Michal Hocko <mhocko@...nel.org>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>, <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] mm: memcontrol: fix swap counter leak on swapout
 from offline cgroup

On Tue, Aug 02, 2016 at 02:42:32PM +0200, Michal Hocko wrote:
> 
> 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).

Yeah, I completely forgot about the !use_hierarchy case. Thanks for
catching this. I'll fix and resend.