Re: [PATCH for-6.0? 1/3] job: Add job_wait_unpaused() for block-job-complete

[Vladimir Sementsov-Ogievskiy]

08.04.2021 20:04, John Snow wrote:
> On 4/8/21 12:58 PM, Vladimir Sementsov-Ogievskiy wrote:
> > job-complete command is async. Can we instead just add a boolean like 
> > job->completion_requested, and set it if job-complete called in STANDBY state, 
> > and on job_resume job_complete will be called automatically if this boolean is 
> > true?
>
> job_complete has a synchronous setup, though -- we lose out on a lot of 
> synchronous error checking in that circumstance.

yes, that's a problem..

> I was not able to audit it to determine that it'd be safe to attempt that setup 
> during a drained section -- I imagine it won't work and will fail, though.
>
> So I thought we'd have to signal completion and run the setup *later*, but what do we do 
> if we get an error then? Does the entire job fail? Do we emit some new event? 
> ("BLOCK_JOB_COMPLETION_FAILED" ?) Is it recoverable?

Isn't it possible even now, that after successful job-complete job still fails 
and we report BLOCK_JOB_COMPLETED with error?

And actually, how much benefit user get from the fact that job-complete may 
fail?

We can make job-complete a simple always-success boolean flag setter like 
job-pause.

And actual completion will be done in background, when possible. And if it 
fail, job just fails, like it does for any background io error. And user have 
to check error/success status of final BLOCK_JOB_COMPLETED anyway.

--
Best regards,
Vladimir