Re: [Qemu-devel] [PATCH v10 09/16] block: Add QMP support for streaming to an intermediate layer

[Eric Blake]

On 10/06/2016 08:02 AM, Alberto Garcia wrote:
> This patch makes the 'device' parameter of the 'block-stream' command
> accept a node name that is not a root node.
> 
> In addition to that, operation blockers will be checked in all
> intermediate nodes between the top and the base node.
> 
> Signed-off-by: Alberto Garcia <address@hidden>
> ---
>  blockdev.c           | 11 +++++++++--
>  qapi/block-core.json | 10 +++++++---
>  2 files changed, 16 insertions(+), 5 deletions(-)
> 

> +++ b/qapi/block-core.json
> @@ -1469,6 +1469,10 @@
>  # 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 chain (but always above the base image; see below) and can 
> be
> +# specified using its device or node name.
> +#
>  # If a base file is specified then sectors are not copied from that base 
> file and
>  # its backing chain.  When streaming completes the image file will have the 
> base
>  # file as its backing file.  This can be used to stream a subset of the 
> backing
> @@ -1480,12 +1484,12 @@
>  # @job-id: #optional identifier for the newly-created block job. If
>  #          omitted, the device name will be used. (Since 2.7)
>  #
> -# @device: the device name or node-name of a root node
> +# @device: the device or node name of the top image
>  #
>  # @base:   #optional the common backing file name
>  #
> -# @backing-file: #optional The backing file string to write into the active
> -#                          layer. This filename is not validated.
> +# @backing-file: #optional The backing file string to write into the top
> +#                          image. This filename is not validated.

No change to the actual introspection. What's the easiest way for
libvirt to learn if the new style command will work, short of actually
trying it to see if it succeeds or fails?  (That may be sufficient, but
the error message quality can often be improved in libvirt if it is
known up front if qemu is new enough rather than taking the 'try and
see' approach and getting stuck with qemu's error message)

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

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