Re: [Qemu-devel] [PATCH v2 00/17] blockdev-add QMP command

[Eric Blake]

On 10/01/2013 07:20 AM, Kevin Wolf wrote:
> This series adds a blockdev-add QMP command and a row of cleanup patches to
> separate legacy -drive/drive_add behaviour from blockdev_init() to the wrapper
> function drive_init().
> 
> v2:
> 
> - Removed I/O throttling and copy-on-read options from the schema: Both are
>   candidates for becoming block filters instead. For the time being, you can
>   use the existing QMP commands in order to enable I/O throttling on a device
>   created with blockdev-add in a second step.

Tolerable as a stop-gap; but doesn't that mean that there is a window
where throttling is not active?  Anything that can restrict block
operations must ultimately be specified atomically up front to avoid a
non-deterministic burst during the race window.  But in the interest of
incremental improvements, I can live with the approach used here, while
still waiting for throttling to be implemented as a true filter device.

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

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