From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Christie Subject: Re: [PATCH] RFC: have dm-mpath use already attached scsi_dh Date: Wed, 22 Apr 2009 08:52:55 -0500 Message-ID: <49EF2137.80708@cs.wisc.edu> References: <1240374806-6043-1-git-send-email-michaelc@cs.wisc.edu> <49EEE071.9060902@suse.de> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <49EEE071.9060902@suse.de> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: Hannes Reinecke Cc: dm-devel@redhat.com, Levy_Jerome@emc.com, linux-scsi@vger.kernel.org List-Id: linux-scsi@vger.kernel.org Hannes Reinecke wrote: > Hi Mike, > > michaelc@cs.wisc.edu wrote: >> From: Mike Christie >> >> If you have a mixed environment of clarriions, where some >> support ALAU and some support PNR, what do you put in >> your multipath.conf? With this patch you do not have to worry about >> it. If those modules are loaded before dm-mpath, then they >> will have attached to the correct devices based on inquiry, alua commands >> and parsing of data buffers (for example in scsi_dh_emc's alua check). >> There is no need for the user to set that info in the multipath.conf. >> And in general since all scsi_dh_modules will attach to the devices >> they work for, we do not need to have users specific this. >> > No. The problem here is the hardware table from scsi_dh is compiled > in and cannot be changed from userland. The multipath.conf OTOH > is purely user-defined and, what's more, the user might have a valid > reason for modifying it. > (EG EMC Clariion can well be run in PNR mode even though ALUA is > active, or the user might want to try ALUA on any as-of-yet unknown > devices) Ah. I misread the code and misunderstood the compat mode. I thought scsi_dh_emc was failing the attach when ALUA support was detected. > > So _not_ allowing multipath to override the device handler setting > will just add to the confusion and makes error tracking even more > difficult. > > So I would prefer the attached patch, it even save to touch > device handler code at all. > Thanks. I think this will work for me. Are you going to push this for 2.6.30?