From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754081AbaCNNXa (ORCPT ); Fri, 14 Mar 2014 09:23:30 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:42572 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753432AbaCNNX3 (ORCPT ); Fri, 14 Mar 2014 09:23:29 -0400 Date: Fri, 14 Mar 2014 06:23:23 -0700 From: Christoph Hellwig To: Mike Snitzer Cc: Christoph Hellwig , Hannes Reinecke , Jeff Moyer , Jens Axboe , Shaohua Li , "linux-kernel@vger.kernel.org" , dm-devel@redhat.com Subject: Re: [PATCH 1/1] block: rework flush sequencing for blk-mq Message-ID: <20140314132323.GA14606@infradead.org> 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> <20140314130021.GA12589@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140314130021.GA12589@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 14, 2014 at 09:00:21AM -0400, Mike Snitzer wrote: > > 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. > > Even _really_ basic dm-multipath testing would've uncovered this bug. But major testing using dm, md and various low-level drivers didn't. Do you really expect everyone to remember to specificly test dm-multipath for a core block change? Without a nicely documented way to do it? That being said I should have remembered that it's special, but even I didn't and I'm sorry about that. > > 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. > > The regression from the commit in question was easily reproduced/tested > using scsi_debug. Just start the multipathd service and any scsi_debug > device in the system will get multipath'd. Really? That sounds a like a bug in the INQUIRY information returned by scsi_debug. Either way please write up these things in Documentation so you can point people at it easily.