Re: [PATCH] [for-10.1] qapi/block-core: derpecate some block-job- APIs

Vladimir Sementsov-Ogievskiy <vsementsov(a)yandex-team.ru&gt; writes: > For change, pause, resume, complete, dismiss and finalize actions > corresponding job- and block-job commands are almost equal. The > difference is in find_block_job_locked() vs find_job_locked() > functions. What's different? > > 1. find_block_job_locked() do check, is found job a block-job. This OK > when moving to more generic API, no needs to document this change. > > 2. find_block_job_locked() reports DeviceNotActive on failure, when > find_job_locked() reports GenericError. So, lets document this > difference in deprecated.txt. Still, for dismiss and finalize errors > are not documented at all, so be silent in deprecated.txt as well. > > Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov(a)yandex-team.ru&gt; > --- > > Hi all! > > That's a continuation of my "[RFC 00/15] block job API"[1], exactly, the > simplest part of it - deprecating block-job-* commands which simply > duplicate job-* ones. > > Note that the old series was started with trying to introduce job-change > command as substitution to both block-job-change (which only can change > mirror copy-mode parameter), and block-job-set-speed. It was rather > complicated and controversial attempt, which latest implemenation was > "[PATCH v3 0/7] introduce job-change qmp command"[2]. > > In [2] Kevin noted, that we'd better follow existing blockdev-reopen > approach of changing options (i.e. specify all options) than introduce a > new one. But, on the other hand, now I'm afraid, that rewriting in > third tools simple call to (old good) block-job-set-speed into > job-change(_all_options_ + changed speed) is too much work just for > "having nice interface". And too much for the only two options we want > to change. > > So, let's just start from something more obvious. Finally, > we can simple keep block-job-set-speed and block-job-change as is, > as they (unlike other block-job-* commands) are not duplicated by > similar job-* commands. > > [1] https://patchew.org/QEMU/20240313150907.623462-1-vsementsov@yandex-team.ru/ > [2] https://patchew.org/QEMU/20241002140616.561652-1-vsementsov@yandex-team.ru/ Thank you for your efforts at making the interfaces cleaner, simpler, and less redundant. > docs/about/deprecated.rst | 31 +++++++++++++++++++++++++++++++ > qapi/block-core.json | 30 ++++++++++++++++++++++++++++++ > 2 files changed, 61 insertions(+) > > diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst > index e2b4f077d4..eed3356359 100644 > --- a/docs/about/deprecated.rst > +++ b/docs/about/deprecated.rst > @@ -148,6 +148,37 @@ options are removed in favor of using explicit ``blockdev-create`` and > ``blockdev-add`` calls. See :doc:`/interop/live-block-operations` for > details. > > +``block-job-pause`` (since 10.1) > +''''''''''''''''''''''''''''''' > + > +Use ``job-pause`` instead. The only difference is that ``job-pause`` > +always reports GenericError on failure when ``block-job-pause`` reports > +DeviceNotActive when block-job is not found. block-job-pause's doc comment: # The operation will pause as soon as possible. No event is emitted # when the operation is actually paused. [...] job-pause's: # The job will pause as soon as possible, which means transitioning # into the PAUSED state if it was RUNNING, or into STANDBY if it was # READY. The corresponding JOB_STATUS_CHANGE event will be emitted. Either one of them is incorrect about event emission, or there is another difference.

> + > +``block-job-resume`` (since 10.1) > +'''''''''''''''''''''''''''''''' > + > +Use ``job-resume`` instead. The only difference is that ``job-resume`` > +always reports GenericError on failure when ``block-job-resume`` reports > +DeviceNotActive when block-job is not found. block-job-resume's doc comment: # This command also clears the error status of the job. Nothing like that job-resume's. Either one of them is incorrect / incomplete about the error status clearance, or there is another difference.

> + > +``block-job-complete`` (since 10.1) > +'''''''''''''''''''''''''''''''''' > + > +Use ``job-complete`` instead. The only difference is that ``job-complete`` > +always reports GenericError on failure when ``block-job-complete`` reports > +DeviceNotActive when block-job is not found. block-job-complete's doc comment: # Manually trigger completion of an active background block operation. # This is supported for drive mirroring, where it also switches the # device to write to the target path only. The ability to complete is # signaled with a BLOCK_JOB_READY event. # # This command completes an active background block operation # synchronously. The ordering of this command's return with the # BLOCK_JOB_COMPLETED event is not defined. Note that if an I/O error # occurs during the processing of this command: 1) the command itself # will fail; 2) the error will be processed according to the # rerror/werror arguments that were specified when starting the # operation. job-complete's: # Manually trigger completion of an active job in the READY state. Is the latter lacking useful information?

> + > +``block-job-dismiss`` (since 10.1) > +''''''''''''''''''''''''''''''''' > + > +Use ``job-dismiss`` instead. block-job-dismiss's doc comment: # For jobs that have already concluded, remove them from the # block-job-query list. This command only needs to be run for jobs # which were started with QEMU 2.12+ job lifetime management # semantics. I figure "started with QEMU 2.12+ job lifetime management semantics" is an awkward way to say "auto-dismiss is false". job-dismiss's doc comment: # Deletes a job that is in the CONCLUDED state. This command only # needs to be run explicitly for jobs that don't have automatic # dismiss enabled. @auto-dismiss defaults to true for jobs that support controlling it: drive-backup, blockdev-backup, block-commit, drive-mirror, blockdev-mirror, block-stream. I guess these are exactly the commands that already existed when we added "QEMU 2.12+ lifetime management". I figure it's always false for the other jobs, but that doesn't seem to be documented anywhere.

> + > +``block-job-finalize`` (since 10.1) > +'''''''''''''''''''''''''''''''''' > + > +Use ``job-finalize`` instead. > + block-job-finalize's doc comment: # Once a job that has manual=true reaches the pending state, it can be # instructed to finalize any graph changes and do any necessary # cleanup via this command. [...] There is no member @manual anywhere in the QAPI schema. I figure this should be @auto-finalize. job-finalize's doc comment: # Instructs all jobs in a transaction (or a single job if it is not # part of any transaction) to finalize any graph changes and do any # necessary cleanup. This command requires that all involved jobs are # in the PENDING state. Nothing on @auto-finalize. @auto-finalize defaults to true for jobs that support controlling it. These are exactly the ones that support @auto-dismiss. I figure @auto-dismiss is always false for the other jobs, but that doesn't seem to be documented anywhere. The only other bits related to @auto-dismiss and @auto-finalize seem to be two states in JobStatus: # @pending: The job has finished its work, but has finalization steps # that it needs to make prior to completing. These changes will # require manual intervention via @job-finalize if auto-finalize # was set to false. These pending changes may still fail. [...] # @concluded: The job has finished all work. If auto-dismiss was set # to false, the job will remain in the query list until it is # dismissed via @job-dismiss. Is it possible to observe @concluded via QMP when @auto-dismiss is on?

What about @pending?

Aside: getting rid of auto-dismiss and auto-finalize some day would be nice.