From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756052AbaCNJa7 (ORCPT ); Fri, 14 Mar 2014 05:30:59 -0400 Received: from cantor2.suse.de ([195.135.220.15]:55310 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755601AbaCNJay (ORCPT ); Fri, 14 Mar 2014 05:30:54 -0400 Message-ID: <5322CC4D.8040509@suse.de> Date: Fri, 14 Mar 2014 10:30:53 +0100 From: Hannes Reinecke User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.1.0 MIME-Version: 1.0 To: Christoph Hellwig , Mike Snitzer CC: Jeff Moyer , Jens Axboe , Shaohua Li , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 1/1] block: rework flush sequencing for blk-mq References: <20140130132620.GA6031@infradead.org> <20140130132630.GB6031@infradead.org> <20140308155240.GA32297@infradead.org> <531B74B6.4070004@suse.de> <20140312102849.GA26509@infradead.org> <20140313161347.GA6598@redhat.com> <20140314092519.GA10139@infradead.org> In-Reply-To: <20140314092519.GA10139@infradead.org> X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/14/2014 10:25 AM, Christoph Hellwig wrote: > On Thu, Mar 13, 2014 at 12:13:47PM -0400, Mike Snitzer wrote: >> Pretty ironic that in the same email that you ask someone to "Let's make >> this a little less personal." you start by asserting upstream >> dm-multipath sees very little testing -- and use your commit that >> recently broke dm-multipath as the basis. Anyway, please exapnd on what >> you feel is broken with upstream dm-multipath. > > Getting a little upset, eh? I didn't say it's broken, I said it gets > very little testing. The regression from me was found like so many > before only after it was backported o some enterprise kernel. > > I think the problem here is two-fold: > a) the hardware you use with dm-multipath isn't widely available. > b) it uses a very special code path in the block layer no one else uses > > a) might be fixable by having some RDAC or similar emulation in qemu if > someone wants to spend the effort. > b) is a bit harder, but we should think hard about it when rewriting the > multipath code to support blk-mq. Talking about which I think trying to > use dm-multipath on any blk-mq device will go horribly crash and boom at > the moment. > That was actually one of my plans, move dm-multipath over to use blk-mq. But then I'd need to discuss with Jens et al how to best achieve this; the current static hctx allocation doesn't play well with multipaths dynamic path management. Cheers, Hannes -- Dr. Hannes Reinecke zSeries & Storage hare@suse.de +49 911 74053 688 SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)