|
From: | Max Reitz |
Subject: | Re: [Qemu-devel] [PATCH] block: add a knob to disable multiwrite_merge |
Date: | Mon, 20 Oct 2014 15:22:34 +0200 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.1.2 |
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
[Prev in Thread] | Current Thread | [Next in Thread] |