[libvirt] [PATCHv6 1/7] qemu: caps: Add capability for change-backing-file command

[Eric Blake]

On 06/26/2014 07:36 AM, Peter Krempa wrote:
> This command allows to change the backing file name recorded in the
> metadata of a qcow (or other) image. The capability also notifies that
> the "block-stream" and "block-commit" commands understand the
> "backing-file" attribute.
> ---
>  src/qemu/qemu_capabilities.c | 2 ++
>  src/qemu/qemu_capabilities.h | 1 +
>  2 files changed, 3 insertions(+)

Upstream qemu.git (and therefore qemu.git) now has everything we need
for this; but I'd still rather wait until after the 1.2.6 release (in
part so that the active-commit stuff can go in first, to minimize rebase
churn):

commit fa40e65622352012dccd435147f28161375a6815
Author: Jeff Cody <jcody at redhat.com>
Date:   Tue Jul 1 09:52:16 2014 +0200

    block: add QAPI command to allow live backing file change

    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.

    [Jeff is offline so I respun this patch in his absence.  Dropped image
    filename since using node-name is preferred and this is a new command.
    No need to introduce the limitations of finding images by filename.
    --Stefan]

    Reviewed-by: Eric Blake <eblake at redhat.com>
    Reviewed-by: Kevin Wolf <kwolf at redhat.com>
    Signed-off-by: Jeff Cody <jcody at redhat.com>
    Signed-off-by: Stefan Hajnoczi <stefanha at redhat.com>


-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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