From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757200Ab2GQWYv (ORCPT ); Tue, 17 Jul 2012 18:24:51 -0400 Received: from mail-pb0-f46.google.com ([209.85.160.46]:49956 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757180Ab2GQWYs (ORCPT ); Tue, 17 Jul 2012 18:24:48 -0400 Date: Tue, 17 Jul 2012 15:24:44 -0700 From: Tejun Heo To: Olof Johansson Cc: 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: <20120717222444.GG24336@google.com> References: <20120717213643.GA24726@quad.lixom.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120717213643.GA24726@quad.lixom.net> 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, 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? Thanks. -- tejun