From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Christie Subject: Re: mechanism for multipath to pass information to hardware handler Date: Sat, 27 Jun 2009 12:48:26 -0500 Message-ID: <4A465B6A.5070507@cs.wisc.edu> References: <1245863681.8709.135.camel@eddie-laptop> <1246043447.3925.64.camel@mulgrave.site> <1246045509.14164.33.camel@chandra-ubuntu> <1246046154.3925.80.camel@mulgrave.site> <1246061016.14164.45.camel@chandra-ubuntu> 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: <1246061016.14164.45.camel@chandra-ubuntu> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: sekharan@linux.vnet.ibm.com Cc: SCSI development list , asson_ronald , "Rafael J. Wysocki" , device-mapper development , Mike Christie , "Benoit, Arthur" List-Id: linux-scsi@vger.kernel.org On 06/26/2009 07:03 PM, Chandra Seetharaman wrote: > On Fri, 2009-06-26 at 14:55 -0500, James Bottomley wrote: >> On Fri, 2009-06-26 at 12:45 -0700, Chandra Seetharaman wrote: >>> Yes, Mike Christie and I were aware of this and it was one of the issue >>> we were trying to resolve before we pushed scsi_dh interface upstream. >>> (It is little complicated as we need the parameters to be set per >>> vendor-product tuple). >>> >>> The original code I ported to scsi_dh interface was from Ed Goggin(who >>> was working for EMC then). IIRC, he was also aware of this issue. >>> >>> When we pushed scsi_dh interface, we did get few of the EMC folks (on >>> Cc) to review/test the code and they did, and this issue was not seen as >>> a problem. >>> >>> We wanted to get back to that issue sometime later, got busy with other >>> things, and it disappeared from my list of things-to-do as the >>> regression was not seen as an issue (till now :)... I will get back to >>> it. >> One way around this might simply be to make the device_handlers create a >> sysfs interface for additional parameters. Then the multipath command > > Yes, having a per device interface is one of the options we considered. > Once we have that defined we can either use sysfs or a scsi_dh_8() API > to achieve the same. > > But we wanted to have it per vendor-product instead of per device, I > don't recall the problems associated with it. Mike(C), do you recall ? > I do not think you want the interface to be per vendor-product in the kernel. You might want some devices with some feature on and some with it off. In userspace we can decide if it is should be per vendor-product or per device, and then have multipath set things up. The kernel interface should probably be more generic. >> can feed them (or in a pinch, users relying on the features can pass >> them in manually). Right at the moment having no possible work around >> does appear to be an issue. > > I will try to roll up a patch soon. >> James >> >> >> -- >> dm-devel mailing list >> dm-devel@redhat.com >> https://www.redhat.com/mailman/listinfo/dm-devel > > -- > To unsubscribe from this list: send the line "unsubscribe linux-scsi" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html