Re: about mirror cancel

[Vladimir Sementsov-Ogievskiy]

16.04.2021 10:11, Max Reitz wrote:
> On 16.04.21 09:05, Max Reitz wrote:
> > On 15.04.21 20:46, Vladimir Sementsov-Ogievskiy wrote:
>
> [...]
>
> > > Note, that if cancelling all in-flight requests on target is wrong on mirror 
> > > cancel, we still don't have real bug, as the only implementation of 
> > > .bdrv_cancel_in_flight is stopping reconnect waiting in nbd driver. So, we'll 
> > > cancel requests only if connection is already lost anyway.
> > >
> > > But that probably means, that correct name of the handler would be 
> > > .bdrv_cancel_in_fligth_requests_that_will_most_probably_fail_anyway()..
> >
> > It’s documentation states that it should cancel all in-flight requests, so it’s 
> > more likely it just isn’t implemented where it could be.
>
> Oh, I now see you added it in the same series.  Well, then I suppose you’re 
> free to change the semantics as you see fit.
>
> But be aware that even cancelling those requests means that you abandon the 
> target.  So it must then fail instead of emitting the COMPLETED event (AFAIR 
> the mirror job emits COMPLETED when cancelled in READY with force=false).

Note that BLOCK_JOB_COMPLETED can indicate failure, it has error field.. 
Interesting, does libvirt aware of it..

> If the user wants the mirror job to create a consistent copy and so cancels it 
> after READY (with force=false), I don’t know whether cancelling those hanging 
> requests is what we want.  If the cancel hangs and the user sees this, they are 
> still free to decide to cancel again with force=true, no?

Right. All right, I'll remake the feature to cancel requests only with 
force=true. Thanks for explanations, and great that I decided to ask.

--
Best regards,
Vladimir