From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
To: Max Reitz <mreitz@redhat.com>, qemu-block@nongnu.org
Cc: qemu-devel@nongnu.org, Kevin Wolf <kwolf@redhat.com>,
John Snow <jsnow@redhat.com>
Subject: Re: [PATCH for-6.1? v2 5/7] job: Add job_cancel_requested()
Date: Tue, 27 Jul 2021 16:04:59 +0300 [thread overview]
Message-ID: <cf6bbb03-b9d6-c24e-3e0b-38d375c855a5@virtuozzo.com> (raw)
In-Reply-To: <20210726144613.954844-6-mreitz@redhat.com>
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 <mreitz@redhat.com>
> ---
> 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));
> 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;
> +}
> +
> +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.
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
--
Best regards,
Vladimir
next prev parent reply other threads:[~2021-07-27 13:07 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-26 14:46 [PATCH for-6.1? v2 0/7] mirror: Handle errors after READY cancel Max Reitz
2021-07-26 14:46 ` [PATCH for-6.1? v2 1/7] mirror: Keep s->synced on error Max Reitz
2021-07-26 14:46 ` [PATCH for-6.1? v2 2/7] mirror: Drop s->synced Max Reitz
2021-07-26 15:26 ` Eric Blake
2021-07-27 11:41 ` Vladimir Sementsov-Ogievskiy
2021-07-26 14:46 ` [PATCH for-6.1? v2 3/7] job: @force parameter for job_cancel_sync{, _all}() Max Reitz
2021-08-03 14:00 ` [PATCH for-6.1? v2 3/7] job: @force parameter for job_cancel_sync{,_all}() Kevin Wolf
2021-07-26 14:46 ` [PATCH for-6.1? v2 4/7] jobs: Give Job.force_cancel more meaning Max Reitz
2021-07-26 21:38 ` Eric Blake
2021-07-27 12:40 ` Vladimir Sementsov-Ogievskiy
2021-07-26 14:46 ` [PATCH for-6.1? v2 5/7] job: Add job_cancel_requested() Max Reitz
2021-07-27 13:04 ` Vladimir Sementsov-Ogievskiy [this message]
2021-07-27 15:39 ` Max Reitz
2021-07-27 15:47 ` Vladimir Sementsov-Ogievskiy
2021-08-02 10:23 ` Max Reitz
2021-08-03 12:35 ` Vladimir Sementsov-Ogievskiy
2021-08-03 14:25 ` Kevin Wolf
2021-08-04 8:07 ` Max Reitz
2021-08-04 10:34 ` Kevin Wolf
2021-08-04 11:00 ` Peter Krempa
2021-08-04 14:15 ` Max Reitz
2021-07-26 14:46 ` [PATCH for-6.1? v2 6/7] mirror: Check job_is_cancelled() earlier Max Reitz
2021-07-27 13:13 ` Vladimir Sementsov-Ogievskiy
2021-07-27 15:40 ` Max Reitz
2021-08-03 14:34 ` Kevin Wolf
2021-08-04 8:25 ` Max Reitz
2021-08-04 9:48 ` Kevin Wolf
2021-08-04 10:12 ` Max Reitz
2021-07-26 14:46 ` [PATCH for-6.1? v2 7/7] iotests: Add mirror-ready-cancel-error test Max Reitz
2021-07-27 13:24 ` Vladimir Sementsov-Ogievskiy
2021-08-03 14:36 ` [PATCH for-6.1? v2 0/7] mirror: Handle errors after READY cancel Kevin Wolf
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