From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933018Ab2GYMJZ (ORCPT ); Wed, 25 Jul 2012 08:09:25 -0400 Received: from cantor2.suse.de ([195.135.220.15]:43766 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932911Ab2GYMJX (ORCPT ); Wed, 25 Jul 2012 08:09:23 -0400 Message-ID: <500FE1F0.3000303@suse.de> Date: Wed, 25 Jul 2012 14:09:20 +0200 From: Hannes Reinecke User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120601 Thunderbird/13.0 MIME-Version: 1.0 To: James Bottomley Cc: Paolo Bonzini , linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org Subject: Re: [PATCH] sd: do not set changed flag on all unit attention conditions References: <1342454772-9018-1-git-send-email-pbonzini@redhat.com> <1342455503.3176.42.camel@dabdike.int.hansenpartnership.com> <50044D56.6000400@redhat.com> <1342511100.3039.9.camel@dabdike.int.hansenpartnership.com> <50052390.7030908@redhat.com> <1342514444.3039.23.camel@dabdike.int.hansenpartnership.com> <5005285E.8060706@redhat.com> <1342516317.3039.35.camel@dabdike.int.hansenpartnership.com> In-Reply-To: <1342516317.3039.35.camel@dabdike.int.hansenpartnership.com> X-Enigmail-Version: 1.4.2 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/17/2012 11:11 AM, James Bottomley wrote: > On Tue, 2012-07-17 at 10:54 +0200, Paolo Bonzini wrote: >> Il 17/07/2012 10:40, James Bottomley ha scritto: >>>>> >>>>> It's not specific to virtio-scsi, in fact I expect that virtio-scsi will >>>>> be almost always used with non-removable disks. >>>>> >>>>> However, QEMU's SCSI target is not used just for virtio-scsi (for >>>>> example it can be used for USB storage), and it lets you mark a disk as >>>>> removable---why? because there exists real hardware that presents itself >>>>> as an SBC removable disk. The only thing that is specific to >>>>> virtualization, is support for online resizing (which generates a unit >>>>> attention condition CAPACITY DATA HAS CHANGED). >>> So what's the problem? If you're doing pass through of a physical disk, >>> we pick up removable from its inquiry string ... a physical removable >>> device doesn't get resized. If you have a virtual disk you want to >>> resize, you don't set the removable flag in the inquiry data. >> >> In practice people will do what you said, and it's not a problem. >> >> However, there's nothing that prevents you from running qemu with a >> removable SCSI disk, and then resizing it. I would like this to work, >> because SBC allows it and there's no reason why it shouldn't. > > There's no such thing in the market today as a removable disk that's > resizeable. Removable disks are for things like backup cartridges and > ageing jazz drives. Worse: most removeable devices today are USB card > readers whose standards compliance varies from iffy to non existent. > Resizeable disks are currently the province of storage arrays. > Ho-hum. I beg to disagree. drivers/scsi/aacraid/aachba.c:2266 /* Do not cache partition table for arrays */ scsicmd->device->removable = 1; To the extend of my knowledge aacraid does this _precisely_ to allow for resizing; in effect every open() will trigger a device revalidation. So I guess by just setting the 'removable' flag you should be okay. You might need to remount it, but that's another story. Cheers, Hannes -- Dr. Hannes Reinecke zSeries & Storage hare@suse.de +49 911 74053 688 SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)