From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753727AbbKYQaq (ORCPT ); Wed, 25 Nov 2015 11:30:46 -0500 Received: from mail-ob0-f182.google.com ([209.85.214.182]:34491 "EHLO mail-ob0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753551AbbKYQal (ORCPT ); Wed, 25 Nov 2015 11:30:41 -0500 Subject: Re: Fwd: 4.4-rc2 crash: block related To: Jan Kara , =?UTF-8?Q?Mika_Penttil=c3=a4?= References: <56554F88.9070305@nextfour.com> <565554EC.7050603@nextfour.com> <20151125083943.GJ25232@quack.suse.cz> Cc: jack@suse.com, LKML , Jeff Moyer From: Jens Axboe Message-ID: <5655E22F.6@kernel.dk> Date: Wed, 25 Nov 2015 09:30:39 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: <20151125083943.GJ25232@quack.suse.cz> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/25/2015 01:39 AM, Jan Kara wrote: > On Wed 25-11-15 08:27:56, Mika Penttilä wrote: >> With recent block layer pull i see a 100% repeatable crash on boot while >> mounting roots (ext4 partition on eMMC, with cfq io scheduler). > > Thanks for report! After some investigation I found out we allocate > elevator specific data in __get_request() only for non-flush requests. And > this is actually required since the flush machinery uses the space in > struct request for something else. Doh. So my patch is just wrong and not > easy to fix since at the time __get_request() is called we are not sure > whether the flush machinery will be used in the end. Jens, please revert > 1b2ff19e6a957b1ef0f365ad331b608af80e932e. Thanks! > > I'm somewhat surprised that you can reliably hit the race where flushing > gets disabled for the device just while the request is in flight. But I > guess during boot it makes some sense. Yeah, that's impressive. I'll revert it and get it sent up before -rc3 is cut. -- Jens Axboe