From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756262Ab2GXSTK (ORCPT ); Tue, 24 Jul 2012 14:19:10 -0400 Received: from mail-pb0-f46.google.com ([209.85.160.46]:55716 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932112Ab2GXSTD (ORCPT ); Tue, 24 Jul 2012 14:19:03 -0400 Date: Tue, 24 Jul 2012 11:18:58 -0700 From: Tejun Heo To: "Maxim V. Patlasov" Cc: Olof Johansson , "axboe@kernel.dk" , "linux-kernel@vger.kernel.org" , "vgoyal@redhat.com" , "torvalds@linux-foundation.org" Subject: Re: [REGRESSION] [PATCH] block: uninitialized ioc->nr_tasks triggers WARN_ON Message-ID: <20120724181858.GB5776@google.com> References: <20120717213643.GA24726@quad.lixom.net> <20120717222444.GG24336@google.com> <500EA4A2.8050806@parallels.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <500EA4A2.8050806@parallels.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Tue, Jul 24, 2012 at 05:35:30PM +0400, Maxim V. Patlasov wrote: > 07/18/2012 02:24 AM, Tejun Heo пишет: > >Hello, Olof. > > > >On Tue, Jul 17, 2012 at 02:36:43PM -0700, Olof Johansson wrote: > >>It seems like the init of ioc->nr_tasks was removed in that patch, > >>so it starts out at 0 instead of 1. > >> > >>Tejun, is the right thing here to add back the init, or should something else > >>be done? > >> > >>The below patch removes the warning, but I haven't done any more extensive > >>testing on it. > >> > >> > >>Signed-off-by: Olof Johansson > >Right, the patch shouldn't have replaced the init. > > > > Acked-by: Tejun Heo > > > >Fortunately, the effect of the bug is limited. ioc->nr_tasks only > >used to veto block cgroup migration if a task has ioc which is shared > >by multiple tasks. Currently, the only known program using CLONE_IO > >is dump and even if somebody migrates some threads of a single dump > >instance to a different block cgroup, the result won't be catastrophic > >although block cgroup policies would become ambiguous. IMHO, it > >should be okay to route this through -stable after 3.5. Jens? > > Please notice that annoying WARN_ON comes from world-visible > ioc_task_link(). So any third-party module using ioc_task_link() > ends up in that clutter in logs. E.g. OpenVZ ploop block-device uses > ioc_task_link(). This should go through block tree. Jens, ping. Thanks. -- tejun