Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S2992524AbbEENpo (ORCPT <rfc822;w@1wt.eu>);
	Tue, 5 May 2015 09:45:44 -0400
Received: from mail-qg0-f46.google.com ([209.85.192.46]:34621 "EHLO
	mail-qg0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S2992494AbbEENp0 (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Tue, 5 May 2015 09:45:26 -0400
Date: Tue, 5 May 2015 09:45:21 -0400
From: Tejun Heo <tj@kernel.org>
To: Vladimir Davydov <vdavydov@parallels.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        Johannes Weiner <hannes@cmpxchg.org>, Michal Hocko <mhocko@suse.cz>,
        Christoph Lameter <cl@linux.com>, Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>, Greg Thelen <gthelen@google.com>,
        linux-mm@kvack.org, cgroups@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] kernfs: do not account ino_ida allocations to memcg
Message-ID: <20150505134521.GL1971@htj.duckdns.org>
References: <fdf631b3fa95567a830ea4f3e19d0b3b2fc99662.1430819044.git.vdavydov@parallels.com>
 <0cf48f4219721952f182715a61910f626d7c4aca.1430819044.git.vdavydov@parallels.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <0cf48f4219721952f182715a61910f626d7c4aca.1430819044.git.vdavydov@parallels.com>
User-Agent: Mutt/1.5.23 (2014-03-12)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 1563
Lines: 35

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@parallels.com>

Man, that's nasty.  For the kernfs part,

Acked-by: Tejun Heo <tj@kernel.org>

Can you please repost this patch w/ Greg KH cc'd?

Thanks.

-- 
tejun
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/