From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757315AbcEDGv7 (ORCPT ); Wed, 4 May 2016 02:51:59 -0400 Received: from ozlabs.org ([103.22.144.67]:51709 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751506AbcEDGv6 (ORCPT ); Wed, 4 May 2016 02:51:58 -0400 Date: Wed, 4 May 2016 16:51:02 +1000 From: Paul Mackerras To: Hannes Reinecke Cc: linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Regression in v4.6-rc due to SCSI multipath change Message-ID: <20160504065101.GA19436@oak.ozlabs.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Current upstream kernels fail to boot on my POWER8 server with multipath SCSI disks and IPR host bus adapters. What happens is that the system finds each disk twice (as normal) and then prints messages like this: [ 2.827761] sd 1:2:4:0: alua: supports implicit TPGS [ 2.827875] sd 1:2:4:0: alua: No device descriptors found [ 2.827923] sd 1:2:4:0: alua: Attach failed (-22) [ 2.827979] device-mapper: table: 253:0: multipath: error attaching hardware handler [ 2.828048] device-mapper: ioctl: error adding target to table Eventually dracut times out (this is with Fedora 23) enters emergency mode. I bisected the problem down to commit 0047220c6c36 ("scsi_dh_alua: use unique device id", 2016-02-19). It seems that this commit adds the restriction that we can only do multipath with disks that have stuff in their VPD page 83 that scsi_vpd_lun_id() can parse. The disks on my server apparently don't. I instrumented scsi_vpd_lun_id() to find out what was going on. The disks on this machine have a vendor-specific designator and a T10 vendor ID based designator, but no designators of types 2, 3 or 8. An example from one disk is: 02 01 00 20 49 42 4d 20 20 20 20 20 49 50 52 2d 30 20 20 20 35 45 43 34 41 42 30 30 30 30 30 30 30 30 32 30 02 00 00 14 30 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 I have a patch that extends scsi_vpd_lun_id() to be able to use the T10 vendor ID based designator, which fixes the problem on my system. I'll post the patch shortly. However, was it really intentional that multipath now can't be used with disks like these, when it worked just fine previously? Paul.