From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:50494 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1422851AbbENWRA (ORCPT ); Thu, 14 May 2015 18:17:00 -0400 Date: Thu, 14 May 2015 15:16:58 -0700 From: akpm@linux-foundation.org To: torvalds@linux-foundation.org, akpm@linux-foundation.org, vdavydov@parallels.com, cl@linux.com, gregkh@linuxfoundation.org, gthelen@google.com, hannes@cmpxchg.org, iamjoonsoo.kim@lge.com, mhocko@suse.cz, penberg@kernel.org, rientjes@google.com, stable@vger.kernel.org, tj@kernel.org Subject: [patch 4/8] kernfs: do not account ino_ida allocations to memcg Message-ID: <55551eda.MoxrRssgopsSTz9+%akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: stable-owner@vger.kernel.org List-ID: From: Vladimir Davydov Subject: kernfs: do not account ino_ida allocations to memcg 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//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 Acked-by: Tejun Heo Cc: Johannes Weiner Cc: Michal Hocko Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Cc: Greg Thelen Cc: Greg Kroah-Hartman Cc: [4.0.x] Signed-off-by: Andrew Morton --- fs/kernfs/dir.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff -puN fs/kernfs/dir.c~kernfs-do-not-account-ino_ida-allocations-to-memcg fs/kernfs/dir.c --- a/fs/kernfs/dir.c~kernfs-do-not-account-ino_ida-allocations-to-memcg +++ a/fs/kernfs/dir.c @@ -518,7 +518,14 @@ static struct kernfs_node *__kernfs_new_ if (!kn) goto err_out1; - ret = ida_simple_get(&root->ino_ida, 1, 0, GFP_KERNEL); + /* + * If the ino of the sysfs entry created for a kmem cache gets + * allocated from an ida layer, which is accounted to the memcg that + * owns the cache, the memcg will get pinned forever. So do not account + * ino ida allocations. + */ + ret = ida_simple_get(&root->ino_ida, 1, 0, + GFP_KERNEL | __GFP_NOACCOUNT); if (ret < 0) goto err_out2; kn->ino = ret; _