Re: [Qemu-devel] [PATCH 00/14] block: Make blockdev-create a job and stable API

[Eric Blake <eblake@redhat.com>]

On 05/25/2018 11:33 AM, Kevin Wolf wrote:
> This changes the x-blockdev-create QMP command so that it doesn't block
> the monitor and the main loop any more, but starts a background job that
> performs the image creation.
> 
> The basic job as implemented here is all that is necessary to make image
> creation asynchronous and to provide a QMP interface that can be marked
> stable, but it still lacks a few features that jobs usually provide: The
> job will ignore pause commands and it doesn't publish progress yet (so
> both current-progress and total-progress stay at 0). These features can
> be added later without breaking compatibility.

Can we at least have total-progress start at 1, and current-progress 
move from 0 to 1 at completion?  Seeing a 0/1 => 1/1 transition is 
better than a divide-by-zero 0/0 ratio throughout the entire job; and 
libvirt doesn't want to add any more special-casing of 0/0 than it 
already has (where it wants to treat that as "job not yet started" 
rather than the more usual sense that if total==current the job is 
hopefully complete).

> 
> At the end of the series, the interface is declared stable and the x-
> prefix is removed.
> 
> Kevin Wolf (14):
>    vdi: Fix vdi_co_do_create() return value
>    vhdx: Fix vhdx_co_create() return value
>    job: Add error message for failing jobs
>    block/create: Make x-blockdev-create a job
>    qemu-iotests: Add VM.get_qmp_events_filtered()
>    qemu-iotests: Add VM.qmp_log()
>    qemu-iotests: Add iotests.img_info_log()
>    qemu-iotests: Rewrite 206 for blockdev-create job
>    qemu-iotests: Rewrite 207 for blockdev-create job
>    qemu-iotests: Rewrite 210 for blockdev-create job
>    qemu-iotests: Rewrite 211 for blockdev-create job
>    qemu-iotests: Rewrite 212 for blockdev-create job
>    qemu-iotests: Rewrite 213 for blockdev-create job
>    block/create: Mark blockdev-create stable

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org