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Date: Tue, 5 May 2015 09:45:21 -0400
From: Tejun Heo <tj@...nel.org>
To: Vladimir Davydov <vdavydov@...allels.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Johannes Weiner <hannes@...xchg.org>,
Michal Hocko <mhocko@...e.cz>,
Christoph Lameter <cl@...ux.com>,
Pekka Enberg <penberg@...nel.org>,
David Rientjes <rientjes@...gle.com>,
Joonsoo Kim <iamjoonsoo.kim@....com>,
Greg Thelen <gthelen@...gle.com>, linux-mm@...ck.org,
cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] kernfs: do not account ino_ida allocations to memcg
On Tue, May 05, 2015 at 12:45:43PM +0300, Vladimir Davydov wrote:
> root->ino_ida is used for kernfs inode number allocations. Since IDA has
> a layered structure, different IDs can reside on the same layer, which
> is currently accounted to some memory cgroup. The problem is that each
> kmem cache of a memory cgroup has its own directory on sysfs (under
> /sys/fs/kernel/<cache-name>/cgroup). If the inode number of such a
> directory or any file in it gets allocated from a layer accounted to the
> cgroup which the cache is created for, the cgroup will get pinned for
> good, because one has to free all kmem allocations accounted to a cgroup
> in order to release it and destroy all its kmem caches. That said we
> must not account layers of ino_ida to any memory cgroup.
>
> Since per net init operations may create new sysfs entries directly
> (e.g. lo device) or indirectly (nf_conntrack creates a new kmem cache
> per each namespace, which, in turn, creates new sysfs entries), an easy
> way to reproduce this issue is by creating network namespace(s) from
> inside a kmem-active memory cgroup.
>
> Signed-off-by: Vladimir Davydov <vdavydov@...allels.com>
Man, that's nasty. For the kernfs part,
Acked-by: Tejun Heo <tj@...nel.org>
Can you please repost this patch w/ Greg KH cc'd?
Thanks.
--
tejun
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