Hi, Stefan:
> The tricky parts are:
>
> 1. Extending the QMP API to support multiple block jobs. Old clients
> only know how to deal with 1 block job but they should continue to
> work.
I think the block-job related qmp commands which are needed to change are as
follows:
1. cmds for job control: block-job-set-speed, block-job-cancel,
block-job-pause, block-job-resume, block-job-complete
2. cmds for job query: query-block-jobs
In order to make sure that old clients keep working, the job control cmds can
add one optional argument of "job_id". If the arg of "job_id" is not assigned,
then the cmd will affect all the running jobs.
The "job_id" may be returned by the corresponding job start command and the
"query-block-jobs" command.
For example:
-> drive-mirror device=drive0 target=/path/to/dest.snap sync=full
<- {u'return': {"job_id": 123}}
-> query-block-jobs
<- {u'return': [{u'busy': True, u'type': u'mirror', u'len': 8589934592,
u'paused': False, u'io-status': u'ok', u'offset': 4483579904, u'device':
u'drive0', u'speed': 1, u'job_id': 123}, {u'busy': True, u'type': u'commit',
u'len': 1073741824, u'paused': False, u'io-status': u'ok', u'offset':
1073741824, u'device': u'drive0', u'speed': 1, u'job_id': 122}]}
->block-job-cancel job_id=123
<- {u'return': {}}
----------
Leiqzhang
Best Regards
> -----Original Message-----
> From: Stefan Hajnoczi [mailto:stefa...@gmail.com]
> Sent: Thursday, April 25, 2013 8:12 PM
> To: Zhangleiqiang
> Cc: Paolo Bonzini; qemu-devel@nongnu.org
> Subject: Re: [Qemu-devel] question about concurrent block job
>
> On Thu, Apr 25, 2013 at 01:59:23AM +0000, Zhangleiqiang wrote:
> > May be the "in_use" flag of "bs" at the "drive" unit is too large.
> > Perhaps
> the "in_use" flag should just lock at the unit of one or some "image(s)" in
> the
> image chain, the "image(s)" needed to be locked are always the ones will be
> write during the job.
> >
> > E.g. "drive_mirror" lock the "snapshot-file", "block-commit" lock the
> > dst
> image of the commit job, etc.
>
> Choosing a finer-grained approach is not too hard.
>
> The tricky parts are:
>
> 1. Extending the QMP API to support multiple block jobs. Old clients
> only know how to deal with 1 block job but they should continue to
> work.
>
> 2. Thinking through all block jobs and their possible interactions.
>
> Stefan
