Re: [Qemu-devel] [PATCH v9 07/11] block: Add QMP support for streaming to an intermediate layer

[Eric Blake]

On 04/04/2016 07:43 AM, Alberto Garcia wrote:
> This patch makes the 'device' parameter of the 'block-stream' command
> accept a node name as well as a device name.
> 
> In addition to that, operation blockers will be checked in all
> intermediate nodes between the top and the base node.
> 
> Since qmp_block_stream() now uses the error from bdrv_lookup_bs() and
> no longer returns DeviceNotFound, iotest 030 is updated to expect
> GenericError instead.
> 
> Signed-off-by: Alberto Garcia <address@hidden>
> ---
> +++ b/qapi/block-core.json
> @@ -1405,6 +1405,10 @@

Context: block-stream

>  # with query-block-jobs.  The operation can be stopped before it has 
> completed
>  # using the block-job-cancel command.
>  #
> +# The node that receives the data is called the top image, can be located
> +# in any part of the whole chain and can be specified using its device
> +# or node name.
> +#

"any part of the whole chain" feels fishy - it has to be ABOVE the base
file.  That is, in a chain A <- B <- C <- D <- E, if I want to set B as
the base, then the top has to be C, D, or E (but not A).

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

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