From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38427) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1W8SJV-0003Tr-3i for qemu-devel@nongnu.org; Wed, 29 Jan 2014 05:24:15 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1W8SJP-0000aA-3z for qemu-devel@nongnu.org; Wed, 29 Jan 2014 05:24:09 -0500 Received: from mx1.redhat.com ([209.132.183.28]:39940) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1W8SJO-0000a1-Sd for qemu-devel@nongnu.org; Wed, 29 Jan 2014 05:24:03 -0500 Date: Wed, 29 Jan 2014 11:23:56 +0100 From: Kevin Wolf Message-ID: <20140129102356.GD2726@dhcp-200-207.str.redhat.com> References: <1390794497-26281-1-git-send-email-famz@redhat.com> <20140128143136.GB1993@stefanha-thinkpad> <20140128165710.GA2907@gate.mains.priv> <20140129084428.GC8739@stefanha-thinkpad.muc.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140129084428.GC8739@stefanha-thinkpad.muc.redhat.com> Subject: Re: [Qemu-devel] [PATCH v12 00/11] Drop in_use from BlockDriverState and enable point-in-time snapshot exporting over NBD List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi Cc: Fam Zheng , rjones@redhat.com, Stefan Hajnoczi , qemu-devel@nongnu.org, armbru@redhat.com, Ian Main , pbonzini@redhat.com Am 29.01.2014 um 09:44 hat Stefan Hajnoczi geschrieben: > On Tue, Jan 28, 2014 at 08:57:11AM -0800, Ian Main wrote: > > On Tue, Jan 28, 2014 at 03:31:36PM +0100, Stefan Hajnoczi wrote: > > > On Mon, Jan 27, 2014 at 11:48:06AM +0800, Fam Zheng wrote: > > > > This series adds for point-in-time snapshot NBD exporting based on > > > > blockdev-backup (variant of drive-backup with existing device as target). > > > > > > > > We get a thin point-in-time snapshot by COW mechanism of drive-backup, and > > > > export it through built in NBD server. The steps are as below: > > > > > > > > 1. (SHELL) qemu-img create -f qcow2 BACKUP.qcow2 > > > > > > > > (Alternatively we can use -o backing_file=RUNNING-VM.img to omit explicitly > > > > providing the size by ourselves, but it's risky because RUNNING-VM.qcow2 is > > > > used r/w by guest. Whether or not setting backing file in the image file > > > > doesn't matter, as we are going to override the backing hd in the next > > > > step) > > > > > > > > 2. (QMP) blockdev-add backing=source-drive file.driver=file file.filename=BACKUP.qcow2 id=target0 if=none driver=qcow2 > > > > > > > > (where source-drive is the running BlockDriverState name for > > > > RUNNING-VM.img. This patch implements "backing=" option to override > > > > backing_hd for added drive) > > > > > > > > 3. (QMP) blockdev-backup device=source-drive sync=none target=target0 > > > > > > > > (this is the QMP command introduced by this series, which use a named > > > > device as target of drive-backup) > > > > > > > > 4. (QMP) nbd-server-add device=target0 > > > > > > > > When image fleecing done: > > > > > > > > 1. (QMP) block-job-cancel device=source-drive > > > > > > > > 2. (HMP) drive_del target0 > > > > > > > > 3. (SHELL) rm BACKUP.qcow2 > > > > > > Seems to work as advertized but do you have qemu-iotests for > > > blockdev-backup and image fleecing in particular? > > > > We have them for drive-backup but not blockdev-backup afaik. Mostly the > > same code but certainly a different API. > > > > It shouldn't be too hard to duplicate the 055 drive-backup code and make > > it a blockdev-backup test. Testing nbd export would be difficult > > however. > > A Python NBD client is pretty easy to implement. Here is a *server* I > wrote for testing a while back: qemu-io should be a good enough NBD client. Kevin