From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH 02/17] scsi_dh_alua: Disable ALUA handling for non-disk devices Date: Mon, 11 May 2015 13:34:51 +0200 Message-ID: <20150511113451.GA4803@lst.de> References: <1430743343-47174-1-git-send-email-hare@suse.de> <1430743343-47174-3-git-send-email-hare@suse.de> <20150511064643.GB30516@lst.de> <555083AF.1000605@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from verein.lst.de ([213.95.11.211]:40023 "EHLO newverein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753047AbbEKLex (ORCPT ); Mon, 11 May 2015 07:34:53 -0400 Content-Disposition: inline In-Reply-To: <555083AF.1000605@suse.de> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Hannes Reinecke Cc: Christoph Hellwig , James Bottomley , linux-scsi@vger.kernel.org On Mon, May 11, 2015 at 12:25:51PM +0200, Hannes Reinecke wrote: > The spec wording doesn't explicitly disallowing you from doing so > (unless you're using referrals). > But in realiter we're using the ALUA device handler only when > multipathing is used, which in turn runs on disk devices only. > So we can limit ourselves to disk devices, too. > > Everything else (like tapes or tape changers) will have to > implement their own logic anyway; tape support in multipathing > with or without ALUA is too horrible to contemplate ... So what is the problem you're trying to solve here? We were attaching to other nodes and so far I haven't heard about that being a problem. Basically we'll disallow I/O for offlines paths to non-disk devices once the ALUA handler is attached, which actually seems useful even without a multipath handler on top. > >> + if (sdev->type != TYPE_DISK && > >> + sdev->type != TYPE_RBC && > >> + sdev->type != TYPE_OSD) { > > > > And does it really allow RBC (but not ZBC)? > > > Thought so, but I'll have to cross-check. > Maybe it's time to implement a 'scsi_is_disk_type()' macro... If the reason to disallow anything that we can't use dm-mpath on both OSD and ZBC in it's current form are excluded. RBC would be included, although I doubt there is a multi ported RBC device available.