From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754841Ab2GQIkw (ORCPT ); Tue, 17 Jul 2012 04:40:52 -0400 Received: from bedivere.hansenpartnership.com ([66.63.167.143]:38771 "EHLO bedivere.hansenpartnership.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753558Ab2GQIkr (ORCPT ); Tue, 17 Jul 2012 04:40:47 -0400 Message-ID: <1342514444.3039.23.camel@dabdike.int.hansenpartnership.com> Subject: Re: [PATCH] sd: do not set changed flag on all unit attention conditions From: James Bottomley To: Paolo Bonzini Cc: linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org Date: Tue, 17 Jul 2012 09:40:44 +0100 In-Reply-To: <50052390.7030908@redhat.com> 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> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3 Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2012-07-17 at 10:34 +0200, Paolo Bonzini wrote: > Il 17/07/2012 09:45, James Bottomley ha scritto: > > On Mon, 2012-07-16 at 19:20 +0200, Paolo Bonzini wrote: > >> Il 16/07/2012 18:18, James Bottomley ha scritto: > >>>>> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c > >>>>> index b583277..6d8ca08 100644 > >>>>> --- a/drivers/scsi/scsi_lib.c > >>>>> +++ b/drivers/scsi/scsi_lib.c > >>>>> @@ -843,8 +843,11 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes) > >>>>> } else if (sense_valid && !sense_deferred) { > >>>>> switch (sshdr.sense_key) { > >>>>> case UNIT_ATTENTION: > >>>>> - if (cmd->device->removable) { > >>>>> - /* Detected disc change. Set a bit > >>>>> + if (cmd->device->removable && > >>>>> + (sshdr.asc == 0x3a || > >>>>> + (sshdr.asc == 0x28 && sshdr.ascq == 0x00))) { > >>>>> + /* "No medium" or "Medium may have changed." > >>>>> + * This means a disc change. Set a bit > >>> This type of change would likely cause a huge cascade of errors in real > >>> removable media devices. Under the MMC standards, which a lot of the > >>> older removable discs seem to follow, UNIT ATTENTION indicates either > >>> medium change or device reset (which we check for and eat lower down); > >>> we can't rely on them giving proper SBC-2 sense codes. If you want to > >>> pretend to be removable media, you have to conform to its standards. > >> > >> Would you accept a patch doing the opposite, i.e. passing some sense > >> codes such as PARAMETERS CHANGED and TARGET OPERATING CONDITIONS HAVE > >> CHANGED? > > > > Could you explain what the problem actually is? It looks like you had a > > reason to mark virtio-scsi as removable, even though it isn't, and now > > you want to add further hacks because being removable doesn't quite > > work. > > 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. James