From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Reinecke Subject: Re: [PATCHv2 0/4] blk-mq support for dm multipath Date: Tue, 28 Oct 2014 19:48:41 +0100 Message-ID: <544FE509.3020207@suse.de> References: <1413589598-17631-1-git-send-email-keith.busch@intel.com> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: Keith Busch Cc: Christoph Hellwig , Jun'ichi Nomura , dm-devel@redhat.com, Mike Snitzer List-Id: dm-devel.ids On 10/28/2014 07:13 PM, Keith Busch wrote: > No comments this time. Did I totally botch this in the wrong direction, > or was the timing bad with the linux con/plumbers that week? > = Basically the latter. We (ie hch and myself) discussed this briefly at LPC, and thought it'd be the right step in the right direction. 'Real' multipath support w/ blk-mq would need some more thought, though. What we've been discussing was to redo the entire I/O submission path: a) pass down I/O _without_ cloning on the current path b) clone the request _for retry_ only. with b) covering retry on a different path and partial I/O submission on the current path. That would have the benefit doing away with the current request/bio cloning. Plus we could even model things like 'preferred' path. Now we only need someone to implement this ... Cheers, Hannes -- = Dr. Hannes Reinecke zSeries & Storage hare@suse.de +49 911 74053 688 SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 N=FCrnberg GF: J. Hawn, J. Guild, F. Imend=F6rffer, HRB 16746 (AG N=FCrnberg)