From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chandra Seetharaman Subject: Re: [RFC][PATCH] Handle multipath paths in a path group properly during pg_init (was "RE: [dm-devel] DM does not activate the paths if there are more than one path in path group during failover") Date: Fri, 14 Nov 2008 11:08:48 -0800 Message-ID: <1226689728.8998.76.camel@chandra-ubuntu> References: <1225944321.14830.1109.camel@chandra-ubuntu> <20081111005920.GN16649@agk.fab.redhat.com> <1226620138.8998.64.camel@chandra-ubuntu> <20081114001205.GQ30569@agk.fab.redhat.com> Reply-To: sekharan@us.ibm.com Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: Received: from e32.co.us.ibm.com ([32.97.110.150]:43186 "EHLO e32.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752042AbYKNTJL (ORCPT ); Fri, 14 Nov 2008 14:09:11 -0500 Received: from d03relay04.boulder.ibm.com (d03relay04.boulder.ibm.com [9.17.195.106]) by e32.co.us.ibm.com (8.13.1/8.13.1) with ESMTP id mAEJ80aw005965 for ; Fri, 14 Nov 2008 12:08:00 -0700 Received: from d03av02.boulder.ibm.com (d03av02.boulder.ibm.com [9.17.195.168]) by d03relay04.boulder.ibm.com (8.13.8/8.13.8/NCO v9.1) with ESMTP id mAEJ8v5W070658 for ; Fri, 14 Nov 2008 12:08:59 -0700 Received: from d03av02.boulder.ibm.com (loopback [127.0.0.1]) by d03av02.boulder.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id mAEJ8tnP023060 for ; Fri, 14 Nov 2008 12:08:56 -0700 In-Reply-To: <20081114001205.GQ30569@agk.fab.redhat.com> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Alasdair G Kergon Cc: device-mapper development , Mike Anderson , Mike Christie , "linux-scsi@vger.kernel.org" , Hannes Reinecke , asson_ronald , Levy_Jerome On Fri, 2008-11-14 at 00:12 +0000, Alasdair G Kergon wrote: > On Thu, Nov 13, 2008 at 03:48:58PM -0800, Chandra Seetharaman wrote: > > The problem reported by Moger Babu was caused due to the architectural > > change made when we moved from dm hardware handler to SCSI hardware > > handler. > > pg_init is single initialisation for the group. > It only needs to happen on one path. Yes, that was my initial response too. dm hardware handlers did not maintain a "state" for each path in which case activating/initializing the controller from one path was sufficient for all the paths connected to the controller to work as expected. SCSI Hardware Handlers maintain a "state" for each path, so that they can fail an I/O at prep_fn, if the path is not an "active" path, which is what lead to the bug Babu saw. > > It sounds to me that what you're adding here is a *per-path* initialisation, > something *separate* from (and additional to) the existing *per-group* pg_init. No, I "replaced" the "per-group" pg_init with "per-path" init. > > Has this patch been tested on EMC? No, we have tested it with LSI RDAC. I will send a separate email to EMC folks (on Cc here) describing the problem and the fix and ask their help in testing. > > Alasdair