Blame SOURCES/kvm-blockjob-Wake-up-BDS-when-job-becomes-idle.patch

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From c48802abf2f0912ce3c34775587f674b037939ac Mon Sep 17 00:00:00 2001
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From: Kevin Wolf <kwolf@redhat.com>
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Date: Wed, 10 Oct 2018 20:21:56 +0100
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Subject: [PATCH 30/49] blockjob: Wake up BDS when job becomes idle
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RH-Author: Kevin Wolf <kwolf@redhat.com>
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Message-id: <20181010202213.7372-18-kwolf@redhat.com>
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Patchwork-id: 82610
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O-Subject: [RHEL-8 qemu-kvm PATCH 27/44] blockjob: Wake up BDS when job becomes idle
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Bugzilla: 1637976
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RH-Acked-by: Max Reitz <mreitz@redhat.com>
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RH-Acked-by: John Snow <jsnow@redhat.com>
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RH-Acked-by: Thomas Huth <thuth@redhat.com>
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In the context of draining a BDS, the .drained_poll callback of block
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jobs is called. If this returns true (i.e. there is still some activity
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pending), the drain operation may call aio_poll() with blocking=true to
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wait for completion.
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As soon as the pending activity is completed and the job finally arrives
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in a quiescent state (i.e. its coroutine either yields with busy=false
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or terminates), the block job must notify the aio_poll() loop to wake
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up, otherwise we get a deadlock if both are running in different
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threads.
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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Reviewed-by: Fam Zheng <famz@redhat.com>
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Reviewed-by: Max Reitz <mreitz@redhat.com>
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(cherry picked from commit 34dc97b9a0e592bc466bdb0bbfe45d77304a72b6)
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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---
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 blockjob.c               | 18 ++++++++++++++++++
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 include/block/blockjob.h | 13 +++++++++++++
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 include/qemu/job.h       |  3 +++
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 job.c                    |  7 +++++++
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 4 files changed, 41 insertions(+)
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diff --git a/blockjob.c b/blockjob.c
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index be5903a..8d27e8e 100644
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--- a/blockjob.c
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+++ b/blockjob.c
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@@ -221,6 +221,22 @@ int block_job_add_bdrv(BlockJob *job, const char *name, BlockDriverState *bs,
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     return 0;
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 }
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+void block_job_wakeup_all_bdrv(BlockJob *job)
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+{
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+    GSList *l;
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+
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+    for (l = job->nodes; l; l = l->next) {
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+        BdrvChild *c = l->data;
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+        bdrv_wakeup(c->bs);
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+    }
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+}
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+
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+static void block_job_on_idle(Notifier *n, void *opaque)
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+{
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+    BlockJob *job = opaque;
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+    block_job_wakeup_all_bdrv(job);
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+}
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+
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 bool block_job_is_internal(BlockJob *job)
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 {
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     return (job->job.id == NULL);
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@@ -419,6 +435,7 @@ void *block_job_create(const char *job_id, const BlockJobDriver *driver,
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     job->finalize_completed_notifier.notify = block_job_event_completed;
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     job->pending_notifier.notify = block_job_event_pending;
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     job->ready_notifier.notify = block_job_event_ready;
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+    job->idle_notifier.notify = block_job_on_idle;
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     notifier_list_add(&job->job.on_finalize_cancelled,
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                       &job->finalize_cancelled_notifier);
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@@ -426,6 +443,7 @@ void *block_job_create(const char *job_id, const BlockJobDriver *driver,
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                       &job->finalize_completed_notifier);
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     notifier_list_add(&job->job.on_pending, &job->pending_notifier);
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     notifier_list_add(&job->job.on_ready, &job->ready_notifier);
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+    notifier_list_add(&job->job.on_idle, &job->idle_notifier);
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     error_setg(&job->blocker, "block device is in use by block job: %s",
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                job_type_str(&job->job));
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diff --git a/include/block/blockjob.h b/include/block/blockjob.h
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index 32c00b7..2290bbb 100644
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--- a/include/block/blockjob.h
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+++ b/include/block/blockjob.h
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@@ -70,6 +70,9 @@ typedef struct BlockJob {
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     /** Called when the job transitions to READY */
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     Notifier ready_notifier;
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+    /** Called when the job coroutine yields or terminates */
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+    Notifier idle_notifier;
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+
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     /** BlockDriverStates that are involved in this block job */
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     GSList *nodes;
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 } BlockJob;
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@@ -119,6 +122,16 @@ int block_job_add_bdrv(BlockJob *job, const char *name, BlockDriverState *bs,
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 void block_job_remove_all_bdrv(BlockJob *job);
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 /**
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+ * block_job_wakeup_all_bdrv:
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+ * @job: The block job
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+ *
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+ * Calls bdrv_wakeup() for all BlockDriverStates that have been added to the
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+ * job. This function is to be called whenever child_job_drained_poll() would
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+ * go from true to false to notify waiting drain requests.
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+ */
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+void block_job_wakeup_all_bdrv(BlockJob *job);
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+
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+/**
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  * block_job_set_speed:
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  * @job: The job to set the speed for.
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  * @speed: The new value
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diff --git a/include/qemu/job.h b/include/qemu/job.h
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index fdaa06f..407d549 100644
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--- a/include/qemu/job.h
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+++ b/include/qemu/job.h
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@@ -156,6 +156,9 @@ typedef struct Job {
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     /** Notifiers called when the job transitions to READY */
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     NotifierList on_ready;
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+    /** Notifiers called when the job coroutine yields or terminates */
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+    NotifierList on_idle;
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+
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     /** Element of the list of jobs */
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     QLIST_ENTRY(Job) job_list;
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diff --git a/job.c b/job.c
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index db53163..5a0ccc7 100644
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--- a/job.c
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+++ b/job.c
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@@ -397,6 +397,11 @@ static void job_event_ready(Job *job)
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     notifier_list_notify(&job->on_ready, job);
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 }
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+static void job_event_idle(Job *job)
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+{
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+    notifier_list_notify(&job->on_idle, job);
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+}
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+
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 void job_enter_cond(Job *job, bool(*fn)(Job *job))
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 {
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     if (!job_started(job)) {
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@@ -442,6 +447,7 @@ static void coroutine_fn job_do_yield(Job *job, uint64_t ns)
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         timer_mod(&job->sleep_timer, ns);
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     }
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     job->busy = false;
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+    job_event_idle(job);
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     job_unlock();
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     qemu_coroutine_yield();
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@@ -860,6 +866,7 @@ static void coroutine_fn job_co_entry(void *opaque)
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     assert(job && job->driver && job->driver->run);
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     job_pause_point(job);
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     job->ret = job->driver->run(job, &job->err);
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+    job_event_idle(job);
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     job->deferred_to_main_loop = true;
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     aio_bh_schedule_oneshot(qemu_get_aio_context(), job_exit, job);
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 }
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-- 
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1.8.3.1
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