From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:47956) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TLlku-0004zC-1M for qemu-devel@nongnu.org; Tue, 09 Oct 2012 22:10:40 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TLlks-00053R-Mn for qemu-devel@nongnu.org; Tue, 09 Oct 2012 22:10:39 -0400 Received: from mx1.redhat.com ([209.132.183.28]:44422) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TLlks-00051R-En for qemu-devel@nongnu.org; Tue, 09 Oct 2012 22:10:38 -0400 Message-ID: <5074D845.8050303@redhat.com> Date: Wed, 10 Oct 2012 10:07:01 +0800 From: Dave Young MIME-Version: 1.0 References: <20120921133031.GA1682@darkstar.nay.redhat.com> <505C768A.5070801@redhat.com> <20120923023709.GA2742@darkstar.nay.redhat.com> <20121005081458.GC1399@stefanha-thinkpad.redhat.com> <50738B8E.1080303@redhat.com> <20121009083120.GA13775@stefanha-thinkpad.redhat.com> In-Reply-To: <20121009083120.GA13775@stefanha-thinkpad.redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v2] virtio-blk: add default serial id List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi Cc: qemu-devel@nongnu.org On 10/09/2012 04:31 PM, Stefan Hajnoczi wrote: > On Tue, Oct 09, 2012 at 10:27:26AM +0800, Dave Young wrote: >> On 10/05/2012 04:14 PM, Stefan Hajnoczi wrote: >> >>> On Sun, Sep 23, 2012 at 10:37:09AM +0800, Dave Young wrote: >>>> For the serial number decreasing issue, I think there's only these two ways to >>>> select, there's no ideal way to resolve this issue. >>>> My use case for this is for the kdump kernel to find proper disks, >>>> after 1st kernel crashing 2nd kernel need find right disk to dump vmcore. >>>> In this case v1 and v2 aproaches are both find to me. >>>> >>>> From my point of view, patch v1 is better though, I think unpluging 100000 is >>>> not a sane use case. It's not likely to happen. >>> >>> I'm not sure auto-assigning serial numbers is a good idea. The guest can use >>> the serial number in /etc/fstab or other places where it expects the serial >>> number to be persistent. >>> >>> Your patch does not provide persistent serial numbers, so a change to the QEMU >>> invocation could result in different serial numbers. The guest will get >>> confused or perhaps refuse to boot. >> >> >> Yes, it introduce confusion, but in this way at least the serial number >> can be persistent across guest reboot. Traditionally ide disks use this >> way as well, such as QEMU_HARDISK_00001, I think guest should not use >> this in /etc/fstab. > > If you don't want to set a persistent serial number, use another mechanism to > identify the disk. For example, Linux has /dev/disk/by-path/ which identifies > virtio-blk PCI adapters, IDE, SCSI disks, etc. > > Does this work for your use case? I have tried this before, but after rebooting (kexec/kdump) the by-path link was not created. It might be udev bug anyway, I'm not sure though. > > Stefan > -- Thanks Dave