Re: [Qemu-devel] [PATCH v6 4/6] commit: support commit active layer

[Eric Blake <eblake@redhat.com>]

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On 11/25/2013 10:45 PM, Fam Zheng wrote:
> If active is top, it will be mirrored to base, (with block/mirror.c
> code), then the image is switched when user completes the block job.
> 
> QMP documentation is updated.
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>
> ---

> +++ b/qapi-schema.json
> @@ -1967,9 +1967,11 @@
>  #
>  # @top:              The file name of the backing image within the image chain,
>  #                    which contains the topmost data to be committed down.
> -#                    Note, the active layer as 'top' is currently unsupported.
>  #
>  #                    If top == base, that is an error.
> +#                    If top == active, the job will not be completed by itself,
> +#                    user needs to complete the job with the block-job-complete
> +#                    command after getting the ready event. (Since 1.8)

s/1.8/2.0/

What happens if the user does block-job-cancel instead of
block-job-complete?  With drive-mirror, that leaves the mirrored drive
as a nice copy at the point in time of the cancel.  I guess with commit,
a cancel just aborts the commit and does not change which image is top.

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


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