Re: [Qemu-devel] [RFC PATCH 0/3] Point-in-time snapshot exporting with drive-backup

[Stefan Hajnoczi]

On Thu, Jun 27, 2013 at 12:06:44PM +0200, Paolo Bonzini wrote:
> Il 27/06/2013 10:17, Stefan Hajnoczi ha scritto:
> >>> > > Il 26/06/2013 05:59, Fam Zheng ha scritto:
> >>> > > This leads to another observation: a sync:'none' block-backup job
> >>> > > probably should never complete, and should instead go on until 
> >>> > > explicit
> >>> > > cancellation.  This is because the job does no background writes, and
> >>> > > thus completion would only happen after the guest has written the 
> >>> > > whole
> >>> > > disk.  Writing the whole disk is rare enough that it will likely cause
> >>> > > bugs in the clients.  It is easier just to never complete the job.
> >>> > > 
> >> > 
> >> > Yes, the sync mode none will simply run forever until cancelled.
> > There is a dedicated command to successfully complete a job:
> > 
> > block-job-complete
> 
> block-job-complete should only be called after a BLOCK_JOB_READY event,
> but when would the backup job raise it?  Immediately after starting?
> 
> There is no behavioral difference in this case between cancel and
> complete in fact as far as I understand, so I think cancelling the job
> would match existing practice better.

Okay.  Ian Main also preferred using block-job-cancel without the
BLOCK_JOB_READY/block-job-complete lifecycle.

Thanks for the input!

Stefan