Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932882AbdCGRNB (ORCPT ); Tue, 7 Mar 2017 12:13:01 -0500 Received: from mail-it0-f42.google.com ([209.85.214.42]:37560 "EHLO mail-it0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932725AbdCGRMf (ORCPT ); Tue, 7 Mar 2017 12:12:35 -0500 Subject: Re: blk: improve order of bio handling in generic_make_request() To: Mike Snitzer References: <87h93blz6g.fsf@notabene.neil.brown.name> <71562c2c-97f4-9a0a-32ec-30e0702ca575@profitbricks.com> <87lgsjj9w8.fsf@notabene.neil.brown.name> <20170307165233.GB30230@redhat.com> Cc: Jack Wang , NeilBrown , LKML , Lars Ellenberg , Kent Overstreet , Pavel Machek , Mikulas Patocka From: Jens Axboe Message-ID: <5cfbdc6b-9ba7-605a-642b-7f625cf5f5b7@kernel.dk> Date: Tue, 7 Mar 2017 10:05:05 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0 MIME-Version: 1.0 In-Reply-To: <20170307165233.GB30230@redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2045 Lines: 57 On 03/07/2017 09:52 AM, Mike Snitzer wrote: > On Tue, Mar 07 2017 at 3:49am -0500, > Jack Wang wrote: > >> >> >> On 06.03.2017 21:18, Jens Axboe wrote: >>> On 03/05/2017 09:40 PM, NeilBrown wrote: >>>> On Fri, Mar 03 2017, Jack Wang wrote: >>>>> >>>>> Thanks Neil for pushing the fix. >>>>> >>>>> We can optimize generic_make_request a little bit: >>>>> - assign bio_list struct hold directly instead init and merge >>>>> - remove duplicate code >>>>> >>>>> I think better to squash into your fix. >>>> >>>> Hi Jack, >>>> I don't object to your changes, but I'd like to see a response from >>>> Jens first. >>>> My preference would be to get the original patch in, then other changes >>>> that build on it, such as this one, can be added. Until the core >>>> changes lands, any other work is pointless. >>>> >>>> Of course if Jens wants a this merged before he'll apply it, I'll >>>> happily do that. >>> >>> I like the change, and thanks for tackling this. It's been a pending >>> issue for way too long. I do think we should squash Jack's patch >>> into the original, as it does clean up the code nicely. >>> >>> Do we have a proper test case for this, so we can verify that it >>> does indeed also work in practice? >>> >> Hi Jens, >> >> I can trigger deadlock with in RAID1 with test below: >> >> I create one md with one local loop device and one remote scsi >> exported by SRP. running fio with mix rw on top of md, force_close >> session on storage side. mdx_raid1 is wait on free_array in D state, >> and a lot of fio also in D state in wait_barrier. >> >> With the patch from Neil above, I can no longer trigger it anymore. >> >> The discussion was in link below: >> http://www.spinics.net/lists/raid/msg54680.html > > In addition to Jack's MD raid test there is a DM snapshot deadlock test, > albeit unpolished/needy to get running, see: > https://www.redhat.com/archives/dm-devel/2017-January/msg00064.html Can you run this patch with that test, reverting your DM workaround? -- Jens Axboe