From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754831Ab2GQIeh (ORCPT ); Tue, 17 Jul 2012 04:34:37 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46865 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754032Ab2GQIe3 (ORCPT ); Tue, 17 Jul 2012 04:34:29 -0400 Message-ID: <50052390.7030908@redhat.com> Date: Tue, 17 Jul 2012 10:34:24 +0200 From: Paolo Bonzini User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120615 Thunderbird/13.0.1 MIME-Version: 1.0 To: James Bottomley CC: 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> In-Reply-To: <1342511100.3039.9.camel@dabdike.int.hansenpartnership.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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). Paolo