From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:54653) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XgCvC-0005VL-DM for qemu-devel@nongnu.org; Mon, 20 Oct 2014 09:22:56 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XgCv6-000274-6g for qemu-devel@nongnu.org; Mon, 20 Oct 2014 09:22:50 -0400 Received: from mx1.redhat.com ([209.132.183.28]:62772) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XgCv5-00026w-W5 for qemu-devel@nongnu.org; Mon, 20 Oct 2014 09:22:44 -0400 Message-ID: <54450C9A.8040807@redhat.com> Date: Mon, 20 Oct 2014 15:22:34 +0200 From: Max Reitz MIME-Version: 1.0 References: <1413785643-20336-1-git-send-email-pl@kamp.de> <5444CED9.8070402@redhat.com> <5444D28F.4010005@kamp.de> <5444D57C.6080409@redhat.com> <5444DDF4.40800@kamp.de> <5444F730.4000003@redhat.com> <5444FD07.6030702@kamp.de> <5444FDBE.9060501@redhat.com> <54450491.7060506@kamp.de> <54450AD7.8000901@redhat.com> <54450BED.6000101@kamp.de> In-Reply-To: <54450BED.6000101@kamp.de> Content-Type: text/plain; charset=iso-8859-15; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] block: add a knob to disable multiwrite_merge List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Lieven , qemu-devel@nongnu.org Cc: kwolf@redhat.com, famz@redhat.com, armbru@redhat.com, stefanha@redhat.com On 20.10.2014 at 15:19, Peter Lieven wrote: > On 20.10.2014 15:15, Max Reitz wrote: >> On 20.10.2014 at 14:48, Peter Lieven wrote: >>> On 20.10.2014 14:19, Max Reitz wrote: >>>> On 2014-10-20 at 14:16, Peter Lieven wrote: >>>>> On 20.10.2014 13:51, Max Reitz wrote: >>>>>> On 2014-10-20 at 12:03, Peter Lieven wrote: >>>>>> [...] >>>>> >>>>> Can you further help here. I think my problem was that I don't >>>>> have access to the commandline options in bdrv_open?! >>>> >>>> You do. It's the "options" QDict. :-) >>> >>> Maybe I just don't get it. >>> >>> If I specify >>> >>> qemu -drive if=virtio,file=image.qcow2,write-merging=off >>> >>> and check with >>> >>> qdict_get_try_bool(options, "write-merging", true); >>> >>> in bdrv_open() directly before bdrv_swap I always get true. >> >> Hm, judging from fprintf(stderr, "%s\n", >> qstring_get_str(qobject_to_json_pretty(QOBJECT(options))));, it's >> there for me (directly after qdict_del(options, "node-name"). The >> output is: >> >> Qemu wrote: >>> { >>> "filename": "image.qcow2" >>> } >>> { >>> "write-merging": "off" >>> } >>> qemu-system-x86_64: -drive >>> if=virtio,file=image.qcow2,write-merging=off: could not open disk >>> image image.qcow2: Block format 'qcow2' used by device 'virtio0' >>> doesn't support the option 'write-merging' >> >> But as you can see, it's a string and not a bool. So the problem is >> that there are (at least) two parameter "types" in qemu: One is just >> giving a QDict, and the other are QemuOpts. QDicts are just the raw >> user input and the user can only input strings, so everything is just >> a string. As far as I know, typing everything correctly is done by >> converting the QDict to a QemuOpts object (as you can see in >> generally every block driver which supports some options (e.g. qcow2) >> and also in blockdev_init(), it's qemu_opts_absorb_qdict()). >> >> Sooo, right, I forgot that. Currently, there are no non-string >> non-block-driver-specific options for mid-tree BDS (in contrast to >> the root BDS, which are parsed in blockdev_init()), so you now have >> the honorable task of introducing such a QemuOptsList along with >> qemu_opts_absorb_qdict() and everything to bdrv_open_common(). *cough* > > I would appreciate if someone with better knowledge of this whole > stuff would start this. Or we postpone this know until all the ongoing > conversions are done. I can try and create some barebone which your patches can then be based on. I probably don't have the knowledge either, but I'm daring enough to do it anyway. ;-) Max