Re: [PATCH for-6.1? v2 4/7] jobs: Give Job.force_cancel more meaning

[Eric Blake]

On Mon, Jul 26, 2021 at 04:46:10PM +0200, Max Reitz wrote:
> We largely have two cancel modes for jobs:
> 
> First, there is actual cancelling.  The job is terminated as soon as
> possible, without trying to reach a consistent result.
> 
> Second, we have mirror in the READY state.  Technically, the job is not
> really cancelled, but it just is a different completion mode.  The job
> can still run for an indefinite amount of time while it tries to reach a
> consistent result.
> 
> We want to be able to clearly distinguish which cancel mode a job is in
> (when it has been cancelled).  We can use Job.force_cancel for this, but
> right now it only reflects cancel requests from the user with
> force=true, but clearly, jobs that do not even distinguish between
> force=false and force=true are effectively always force-cancelled.
> 
> So this patch has Job.force_cancel signify whether the job will
> terminate as soon as possible (force_cancel=true) or whether it will
> effectively remain running despite being "cancelled"
> (force_cancel=false).
> 
> To this end, we let jobs that provide JobDriver.cancel() tell the
> generic job code whether they will terminate as soon as possible or not,
> and for jobs that do not provide that method we assume they will.
> 
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
>  include/qemu/job.h | 11 ++++++++++-
>  block/backup.c     |  3 ++-
>  block/mirror.c     | 24 ++++++++++++++++++------
>  job.c              |  6 +++++-
>  4 files changed, 35 insertions(+), 9 deletions(-)
>

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
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