From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bart Van Assche Subject: Re: [PATCHv2] sd: retry READ CAPACITY for ALUA state transition Date: Tue, 7 Jul 2015 13:48:26 -0700 Message-ID: <559C3B1A.3020002@sandisk.com> References: <1436181130-82905-1-git-send-email-hare@suse.de> <559A9B23.4020705@sandisk.com> <1436216244.6241.7.camel@HansenPartnership.com> <559B6F24.6020804@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-bn1bon0072.outbound.protection.outlook.com ([157.56.111.72]:64170 "EHLO na01-bn1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932704AbbGGUsa (ORCPT ); Tue, 7 Jul 2015 16:48:30 -0400 In-Reply-To: <559B6F24.6020804@suse.de> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Hannes Reinecke , James Bottomley Cc: Christoph Hellwig , "linux-scsi@vger.kernel.org" On 07/06/2015 11:18 PM, Hannes Reinecke wrote: > However, to handle the above case correctly we would need to keep > track of the entire multipath topology, to figure out which devices > belong to that relative target port and might need to be updated > (there might be several paths in standby, and we will have sent the > RTPG only for one of them). > Patches for that are not done yet, so I thought the above patch > would be a simple stop-gap measure. Hello Hannes, Are you sure that keeping track of the entire multipath topology would be required to implement what I proposed ? In the patch "scsi_dh_alua: Use separate alua_port_group structure" (http://thread.gmane.org/gmane.linux.scsi/101388/focus=101380) I see that the new scsi_dh_alua code keeps track of the target port group (TPG) ID and relative target port (RTP) ID. As you know this information can be queried for each LUN via the Device Identification VPD page. How about caching the TPG and RTP IDs per LUN such that the scsi_dh_alua code can figure out which LUNs are associated with which target ports by iterating over the known LUNs ? Thanks, Bart.