From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60706) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XgDJH-0002TB-Oa for qemu-devel@nongnu.org; Mon, 20 Oct 2014 09:47:49 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XgDJB-0003bM-NL for qemu-devel@nongnu.org; Mon, 20 Oct 2014 09:47:43 -0400 Received: from mx-v6.kamp.de ([2a02:248:0:51::16]:35503 helo=mx01.kamp.de) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XgDJB-0003ai-DZ for qemu-devel@nongnu.org; Mon, 20 Oct 2014 09:47:37 -0400 Message-ID: <54451273.8040007@kamp.de> Date: Mon, 20 Oct 2014 15:47:31 +0200 From: Peter Lieven MIME-Version: 1.0 References: <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> <54450C9A.8040807@redhat.com> <20141020133100.GJ3585@noname.redhat.com> In-Reply-To: <20141020133100.GJ3585@noname.redhat.com> Content-Type: text/plain; charset=windows-1252; 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: Kevin Wolf , Max Reitz Cc: famz@redhat.com, qemu-devel@nongnu.org, stefanha@redhat.com, armbru@redhat.com On 20.10.2014 15:31, Kevin Wolf wrote: > Am 20.10.2014 um 15:22 hat Max Reitz geschrieben: >> 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. ;-) > Actually I have some patches somewhere [1] that introduce a QemuOpts for > bdrv_open_common(). I intended to use that for cache modes, but as I > explained in our KVM Forum presentation, it's not quite as easy as I > thought it would be and so the patch series isn't ready yet. > > Anyway, having the QemuOpts there for driver-independent options is > probably the way to go. Feel free to remove the caching from my > patch and keep only the node-name part. Then it can be a preparatory > patch for your series where you simply add a new option to the list. > > Kevin > > [1] http://repo.or.cz/w/qemu/kevin.git/commitdiff/9c22aee04cf0bdf6a3858340bc6ff27d6805254f Thank you. Would it be legit to recycle qemu_common_drive_opts from blockdev.c for this? Peter