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Re: [Qemu-devel] [PATCH v7 for 2.1 4/4] block: add QAPI command to allow
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PATCH v7 for 2.1 4/4] block: add QAPI command to allow live backing file change |
Date: |
Wed, 25 Jun 2014 13:52:25 -0600 |
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Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 |
On 06/25/2014 01:40 PM, Jeff Cody wrote:
> This allows a user to make a live change to the backing file recorded in
> an open image.
>
> The image file to modify can be specified 2 ways:
>
> 1) image filename
> 2) image node-name
>
> Note: this does not cause the backing file itself to be reopened; it
> merely changes the backing filename in the image file structure, and
> in internal BDS structures.
>
> It is the responsibility of the user to pass a filename string that
> can be resolved when the image chain is reopened, and the filename
> string is not validated.
>
> A good analogy for this command is that it is a live version of
> 'qemu-img rebase -u', with respect to changing the backing file string.
For 2.1, did we want to limit this command to only affecting the active
layer (and failing if it was attempted on a backing file), in order to
simplify dealing with op-blocker work? Having the command exist, even
if it is limited in nature, is all the more libvirt wants right now; and
it's easier to relax a constraint in a future release than it is to
release something now and have to keep it working even after we rework
op-blockers in the future.
>
> Reviewed-by: Eric Blake <address@hidden>
> Signed-off-by: Jeff Cody <address@hidden>
I'm still okay with this patch as-is, if we are okay with the ability to
rename the backing file of a non-active node.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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