Re: [Qemu-devel] question about concurrent block job

[Stefan Hajnoczi]

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