From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:35412) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SfAyf-0003ys-3j for qemu-devel@nongnu.org; Thu, 14 Jun 2012 10:24:57 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1SfAyV-0001Kz-7Z for qemu-devel@nongnu.org; Thu, 14 Jun 2012 10:24:48 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59497) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SfAyU-0001KI-Vw for qemu-devel@nongnu.org; Thu, 14 Jun 2012 10:24:39 -0400 Message-ID: <4FD9F421.9030406@redhat.com> Date: Thu, 14 Jun 2012 16:24:33 +0200 From: Kevin Wolf MIME-Version: 1.0 References: <1339598189-17933-1-git-send-email-wdongxu@linux.vnet.ibm.com> <1339598189-17933-4-git-send-email-wdongxu@linux.vnet.ibm.com> <4FD9C24A.70906@redhat.com> <4FD9F104.1010209@redhat.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 4/6] qemu-img: add-cow will not support convert List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Dong Xu Wang Cc: Stefan Hajnoczi , qemu-devel@nongnu.org Am 14.06.2012 16:17, schrieb Dong Xu Wang: > On Thu, Jun 14, 2012 at 10:11 PM, Kevin Wolf wrote: >> Am 14.06.2012 16:06, schrieb Dong Xu Wang: >>> On Thu, Jun 14, 2012 at 6:51 PM, Kevin Wolf wrote: >>>> Am 13.06.2012 16:36, schrieb Dong Xu Wang: >>>>> add-cow file can't live alone, must together will image_file and backing_file. >>>>> If we implement qemu-img convert operation for add-cow file format, we must >>>>> create image_file and backing_file manually, that will be confused for users, >>>>> so we just ignore add-cow format while doing converting. >>>>> >>>>> Signed-off-by: Dong Xu Wang >>>> >>>> NACK. >>>> >>>> This stupid "let's drop the feature, it might confuse users" attitude is >>>> known from Gnome, but not from qemu. >>>> >>>> There's no technical reason to forbid it and anyone who manages to >>>> create a valid add-cow image will also be able to specify the very same >>>> options to a convert command. Also, having image format specific code in >>>> qemu-img is evil. >>>> >>> >>> If I implement add-cow convert command, I am wondering which method should >>> I use: >>> 1) create add-cow, and its backing_file, and its image_file, then we >>> need 3 files. >>> 2) create add-cow(with all bitmap marked to allocated), and its >>> image_file, then we >>> need 2 files. >>> >>> 2) will be easier, I should let .add-cow file can live only with >>> image_file, without backing_file. >>> >>> I think both 1) and 2) need add code to qemu-img.c. Or I will have to create >>> image_file automaticly in add_cow_create function. >>> >>> Can you give some comments on how to implement convert? Thanks. >> >> Just leave it alone and it will work. >> >> qemu-img convert takes the same options as qemu-img create. So like for >> any other image you specify the backing file with -b or -o backing_file, >> and for add-cow images to be successfully created you also need to >> specify -o image_file. >> > "-o image_file", the image_file should be precreated? Or I should created it > manually? Yes, it must already exist. Just like with qemu-img create. To convert an existing qcow2 image that has a backing file 'base.img' to an add-cow image, you would use something like: $ qemu-img create -f raw target.img 4G $ qemu-img convert -O add-cow -o image_file=target.img -B base.img source.qcow2 target.add-cow Kevin