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v2 5/7] job: Add job_cancel_requested() To: Vladimir Sementsov-Ogievskiy , qemu-block@nongnu.org References: <20210726144613.954844-1-mreitz@redhat.com> <20210726144613.954844-6-mreitz@redhat.com> <79105dcc-eaa3-086b-34ed-b66eef584a3b@virtuozzo.com> From: Max Reitz Message-ID: <6ae8d39e-62cc-bd8c-c78e-d2747eb83715@redhat.com> Date: Mon, 2 Aug 2021 12:23:57 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <79105dcc-eaa3-086b-34ed-b66eef584a3b@virtuozzo.com> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mreitz@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Received-SPF: pass client-ip=170.10.133.124; envelope-from=mreitz@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.699, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.08, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , John Snow , qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 27.07.21 17:47, Vladimir Sementsov-Ogievskiy wrote: > 27.07.2021 18:39, Max Reitz wrote: >> On 27.07.21 15:04, Vladimir Sementsov-Ogievskiy wrote: >>> 26.07.2021 17:46, Max Reitz wrote: >>>> Most callers of job_is_cancelled() actually want to know whether >>>> the job >>>> is on its way to immediate termination.  For example, we refuse to >>>> pause >>>> jobs that are cancelled; but this only makes sense for jobs that are >>>> really actually cancelled. >>>> >>>> A mirror job that is cancelled during READY with force=false should >>>> absolutely be allowed to pause.  This "cancellation" (which is >>>> actually >>>> a kind of completion) may take an indefinite amount of time, and so >>>> should behave like any job during normal operation.  For example, with >>>> on-target-error=stop, the job should stop on write errors. (In >>>> contrast, force-cancelled jobs should not get write errors, as they >>>> should just terminate and not do further I/O.) >>>> >>>> Therefore, redefine job_is_cancelled() to only return true for jobs >>>> that >>>> are force-cancelled (which as of HEAD^ means any job that >>>> interprets the >>>> cancellation request as a request for immediate termination), and add >>>> job_cancel_request() as the general variant, which returns true for >>>> any >>> >>> job_cancel_requested() >>> >>>> jobs which have been requested to be cancelled, whether it be >>>> immediately or after an arbitrarily long completion phase. >>>> >>>> Buglink: https://gitlab.com/qemu-project/qemu/-/issues/462 >>>> Signed-off-by: Max Reitz >>>> --- >>>>   include/qemu/job.h |  8 +++++++- >>>>   block/mirror.c     | 10 ++++------ >>>>   job.c              |  7 ++++++- >>>>   3 files changed, 17 insertions(+), 8 deletions(-) >>>> >>>> diff --git a/include/qemu/job.h b/include/qemu/job.h >>>> index 8aa90f7395..032edf3c5f 100644 >>>> --- a/include/qemu/job.h >>>> +++ b/include/qemu/job.h >>>> @@ -436,9 +436,15 @@ const char *job_type_str(const Job *job); >>>>   /** Returns true if the job should not be visible to the >>>> management layer. */ >>>>   bool job_is_internal(Job *job); >>>>   -/** Returns whether the job is scheduled for cancellation. */ >>>> +/** Returns whether the job is being cancelled. */ >>>>   bool job_is_cancelled(Job *job); >>>>   +/** >>>> + * Returns whether the job is scheduled for cancellation (at an >>>> + * indefinite point). >>>> + */ >>>> +bool job_cancel_requested(Job *job); >>>> + >>>>   /** Returns whether the job is in a completed state. */ >>>>   bool job_is_completed(Job *job); >>>>   diff --git a/block/mirror.c b/block/mirror.c >>>> index e93631a9f6..72e02fa34e 100644 >>>> --- a/block/mirror.c >>>> +++ b/block/mirror.c >>>> @@ -936,7 +936,7 @@ static int coroutine_fn mirror_run(Job *job, >>>> Error **errp) >>>>           /* Transition to the READY state and wait for complete. */ >>>>           job_transition_to_ready(&s->common.job); >>>>           s->actively_synced = true; >>>> -        while (!job_is_cancelled(&s->common.job) && >>>> !s->should_complete) { >>>> +        while (!job_cancel_requested(&s->common.job) && >>>> !s->should_complete) { >>>>               job_yield(&s->common.job); >>>>           } >>>>           s->common.job.cancelled = false; >>>> @@ -1043,7 +1043,7 @@ static int coroutine_fn mirror_run(Job *job, >>>> Error **errp) >>>>               } >>>>                 should_complete = s->should_complete || >>>> -                job_is_cancelled(&s->common.job); >>>> + job_cancel_requested(&s->common.job); >>>>               cnt = bdrv_get_dirty_count(s->dirty_bitmap); >>>>           } >>>>   @@ -1087,7 +1087,7 @@ static int coroutine_fn mirror_run(Job >>>> *job, Error **errp) >>>>           trace_mirror_before_sleep(s, cnt, >>>> job_is_ready(&s->common.job), >>>>                                     delay_ns); >>>>           job_sleep_ns(&s->common.job, delay_ns); >>>> -        if (job_is_cancelled(&s->common.job) && >>>> s->common.job.force_cancel) { >>>> +        if (job_is_cancelled(&s->common.job)) { >>>>               break; >>>>           } >>>>           s->last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME); >>>> @@ -1099,9 +1099,7 @@ immediate_exit: >>>>            * or it was cancelled prematurely so that we do not >>>> guarantee that >>>>            * the target is a copy of the source. >>>>            */ >>>> -        assert(ret < 0 || >>>> -               (s->common.job.force_cancel && >>>> -                job_is_cancelled(&s->common.job))); >>>> +        assert(ret < 0 || job_is_cancelled(&s->common.job)); >> >> (As a note, I hope this does the job regarding your suggestions for >> patch 4. :)) >> >>>>           assert(need_drain); >>>>           mirror_wait_for_all_io(s); >>>>       } >>>> diff --git a/job.c b/job.c >>>> index e78d893a9c..dba17a680f 100644 >>>> --- a/job.c >>>> +++ b/job.c >>>> @@ -216,6 +216,11 @@ const char *job_type_str(const Job *job) >>>>   } >>>>     bool job_is_cancelled(Job *job) >>>> +{ >>>> +    return job->cancelled && job->force_cancel; >>> >>> can job->cancelled be false when job->force_cancel is true ? I think >>> not and worth an assertion here. Something like >>> >>> if (job->force_cancel) { >>>    assert(job->cancelled); >>>    return true; >>> } >>> >>> return false; >> >> Sounds good, why not. >> >>> >>>> +} >>>> + >>>> +bool job_cancel_requested(Job *job) >>>>   { >>>>       return job->cancelled; >>>>   } >>>> @@ -1015,7 +1020,7 @@ void job_complete(Job *job, Error **errp) >>>>       if (job_apply_verb(job, JOB_VERB_COMPLETE, errp)) { >>>>           return; >>>>       } >>>> -    if (job_is_cancelled(job) || !job->driver->complete) { >>>> +    if (job_cancel_requested(job) || !job->driver->complete) { >>>>           error_setg(errp, "The active block job '%s' cannot be >>>> completed", >>>>                      job->id); >>>>           return; >>>> >>> >>> I think it's a correct change, although there may be unexpected >>> side-effects, it's hard to imagine all consequences of changing >>> job_is_cancelled() semantics called in several places in job.c. > > For example: so we now don't set -ECANCELED in job_update_rc for > soft-cancel.. > > This mean that job_finalize_single() will call job_commit instead of > job_abort, and job_commit may do some graph changes, which shouldn't > happen for soft-cancel So the question is when these two conditions come into play. There are two places that set job->ret to ECANCELED if the job is cancelled, namely job_update_rc(), and job_finish_sync(). job_finish_sync() will do so only after the job has been completed, which requires the job to either have been aborted (i.e. ret is non-zero anyway) or job_completed() to have been called. job_completed() is called by job_exit(), which is run after the job’s main loop has exited.  If mirror is soft-cancelled, mirror_run() will clear s->common.job.cancelled before returning, so job_finish_sync() will not see the job as cancelled. job_update_rc() is called from three places: job_finalize_single(): Asserts that job_is_completed(), so the same reasoning as for job_finish_sync() applies. job_prepare(): Called by job_do_finalize(), which can only happen when the job is completed.  (JobVerbTable only allows finalization when the job is PENDING, which is a state where job_is_completed() is true, i.e. after mirror_run().) job_completed(): Same reasoning as for job_finish_sync(). So it looks to me like these places that set job->ret to ECANCELED if the job has been cancelled do not consider a soft-cancelled mirror job to have been cancelled, which makes using job_is_cancelled() instead of job_cancel_requested() correct there. (And most likely, we can drop the `.cancelled = false` statements from the mirror job in turn.) Max