From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Reinecke Subject: Re: [PATCH] sd: do not set changed flag on all unit attention conditions Date: Wed, 25 Jul 2012 14:09:20 +0200 Message-ID: <500FE1F0.3000303@suse.de> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <1342516317.3039.35.camel@dabdike.int.hansenpartnership.com> Sender: linux-kernel-owner@vger.kernel.org To: James Bottomley Cc: Paolo Bonzini , linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org List-Id: linux-scsi@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-sc= si 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 d= isk 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 removab= le >>> 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 wor= k, >> because SBC allows it and there's no reason why it shouldn't. >=20 > There's no such thing in the market today as a removable disk that's > resizeable. Removable disks are for things like backup cartridges an= d > ageing jazz drives. Worse: most removeable devices today are USB car= d > readers whose standards compliance varies from iffy to non existent. > Resizeable disks are currently the province of storage arrays. >=20 Ho-hum. I beg to disagree. drivers/scsi/aacraid/aachba.c:2266 /* Do not cache partition table for arrays */ scsicmd->device->removable =3D 1; To the extend of my knowledge aacraid does this _precisely_ to allow for resizing; in effect every open() will trigger a device revalidation= =2E 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 --=20 Dr. Hannes Reinecke zSeries & Storage hare@suse.de +49 911 74053 688 SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 N=C3=BCrnberg GF: J. Hawn, J. Guild, F. Imend=C3=B6rffer, HRB 16746 (AG N=C3=BCrnberg= )