From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56159) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XgD1S-000858-P2 for qemu-devel@nongnu.org; Mon, 20 Oct 2014 09:29:27 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XgD1I-0004IZ-GI for qemu-devel@nongnu.org; Mon, 20 Oct 2014 09:29:18 -0400 Received: from mx-v6.kamp.de ([2a02:248:0:51::16]:36643 helo=mx01.kamp.de) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XgD1I-0004IF-6g for qemu-devel@nongnu.org; Mon, 20 Oct 2014 09:29:08 -0400 Message-ID: <54450E20.1000409@kamp.de> Date: Mon, 20 Oct 2014 15:29:04 +0200 From: Peter Lieven 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> <54450C9A.8040807@redhat.com> In-Reply-To: <54450C9A.8040807@redhat.com> 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: Max Reitz , qemu-devel@nongnu.org Cc: kwolf@redhat.com, famz@redhat.com, armbru@redhat.com, stefanha@redhat.com On 20.10.2014 15:22, Max Reitz wrote: > 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. ;-) Thank you. Peter