From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751913Ab2CPEV5 (ORCPT ); Fri, 16 Mar 2012 00:21:57 -0400 Received: from mga09.intel.com ([134.134.136.24]:40960 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750751Ab2CPEV4 (ORCPT ); Fri, 16 Mar 2012 00:21:56 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.67,352,1309762800"; d="scan'208";a="118211861" Date: Fri, 16 Mar 2012 12:20:36 +0800 From: Fengguang Wu To: Tejun Heo Cc: Jens Axboe , Vivek Goyal , LKML Subject: Re: [PATCH block/for-3.4/core] cfq: fix cfqg ref handling when BLK_CGROUP && !CFQ_GROUP_IOSCHED Message-ID: <20120316042036.GA32728@localhost> References: <20120315094945.GA3205@localhost> <20120315163546.GA32137@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120315163546.GA32137@google.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 15, 2012 at 09:35:46AM -0700, Tejun Heo wrote: > When BLK_CGROUP is enabled but CFQ_GROUP_IOSCHED is, cfq ends up > calling blkg_get/put() on dummy cfqg leading to the following crash. > > BUG: unable to handle kernel NULL pointer dereference at 00000000000000b0 > IP: [] cfq_init_queue+0x258/0x430 > Reported-by: Fengguang Wu > Signed-off-by: Tejun Heo Tested-by: Fengguang Wu Thanks for the quick fix! > --- > Yeap, forgot to test that config combination. Fengguang, can you > please test this patch? Jens, once Fengguang confirms the fix, can > you please apply this on top of for-3.4/core along with the pending > stats updates?