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Re: [Qemu-devel] [PATCH V4 4/4] Change default to qcow2 for sync mode no
From: |
Ian Main |
Subject: |
Re: [Qemu-devel] [PATCH V4 4/4] Change default to qcow2 for sync mode none. |
Date: |
Thu, 18 Jul 2013 11:03:39 -0700 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Thu, Jul 18, 2013 at 11:32:52AM -0600, Eric Blake wrote:
> On 07/18/2013 11:27 AM, Eric Blake wrote:
>
> >> if (!has_format) {
> >> - format = mode == NEW_IMAGE_MODE_EXISTING ? NULL :
> >> bs->drv->format_name;
> >> + format = mode == NEW_IMAGE_MODE_EXISTING ? NULL : "qcow2";
> >
> > Is this the right thing to do? Or should we do:
> >
> > if (!has_format) {
> > if (mode == NEW_IMAGE_MODE_EXISTING) {
> > format = NULL;
> > } else {
> > format = bs->drv->format_name ?: "qcow2";
> > }
> > }
> >
> > That is, I think we should default to doing a backup in the format given
> > by the original (what if the original is qed, which also supports
> > backing files), and only use qcow2 when there is no guidance whatsoever.
> >
> > But in practice, I don't care
>
> Well, I _DO_ care about one thing - make sure that the qapi-schema.json
> page accurately documents how this variable is defaulted for callers
> that don't care about the implications of omitting a format.
>
> Or we could simplify life by making 'format' mandatory for drive-backup;
> it was optional for 'drive-mirror' due to incremental implementation,
> but for 'drive-backup', we still have the opportunity to do things right
> from the first release.
Ah, I did make a doc change, I must have forgotten to add it.
I'm all for making format mandatory if that is ok with everyone. Maybe
that is the best solution.
Ian
- [Qemu-devel] [PATCH V4 0/4] Implement sync modes for drive-backup., Ian Main, 2013/07/17
- [Qemu-devel] [PATCH V4 3/4] Add backing drive while performing backup., Ian Main, 2013/07/17
- [Qemu-devel] [PATCH V4 1/4] Implement sync modes for drive-backup., Ian Main, 2013/07/17
- [Qemu-devel] [PATCH V4 2/4] Add tests for sync modes 'TOP' and 'NONE', Ian Main, 2013/07/17
- [Qemu-devel] [PATCH V4 4/4] Change default to qcow2 for sync mode none., Ian Main, 2013/07/17
- Re: [Qemu-devel] [PATCH V4 4/4] Change default to qcow2 for sync mode none., Ian Main, 2013/07/18