Message ID | 20171011191317.24157-4-dgilbert@redhat.com |
---|---|
State | New |
Headers | show |
Series | migration: pause-before-device | expand |
On Wed, Oct 11, 2017 at 08:13:13PM +0100, Dr. David Alan Gilbert (git) wrote: > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com> > > Wait for a semaphore before completing the migration, > if the previously added capability was enabled. > > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com> > --- > migration/migration.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++ > migration/migration.h | 3 +++ > 2 files changed, 50 insertions(+) > > diff --git a/migration/migration.c b/migration/migration.c > index e1a87c3d23..b411a7bb63 100644 > --- a/migration/migration.c > +++ b/migration/migration.c > @@ -1967,6 +1967,46 @@ fail: > } > > /** > + * migration_maybe_pause: Pause if required to by migrate_pause_before_device > + * called with the iothread locked > + * Returns: 0 on success > + */ > +static int migration_maybe_pause(MigrationState *s, int *current_active_state) > +{ > + int ret; > + if (!migrate_pause_before_device()) { > + return 0; > + } > + ret = bdrv_inactivate_all(); My understanding is that the crash was caused by mirrored block device IO triggered after the inactivation, then... should we do this after waiting for the semaphore (possibly at [1] below) to make sure the block jobs are completed? Or did I miss anything? > + if (ret) { > + error_report("%s: bdrv_inactivate_all() failed (%d)", > + __func__, ret); > + return ret; > + } > + > + s->block_inactive = true; > + > + /* Since leaving this state is not atomic with posting the semaphore > + * it's possible that someone could have issued multiple migrate_continue > + * and the semaphore is incorrectly positive at this point; > + * the docs say it's undefined to reinit a semaphore that's already > + * init'd, so use timedwait to eat up any existing posts. > + */ > + while (qemu_sem_timedwait(&s->pause_sem, 1) == 0); > + > + qemu_mutex_unlock_iothread(); > + migrate_set_state(&s->state, *current_active_state, > + MIGRATION_STATUS_PAUSE_BEFORE_DEVICE); > + qemu_sem_wait(&s->pause_sem); [1] > + migrate_set_state(&s->state, MIGRATION_STATUS_PAUSE_BEFORE_DEVICE, > + MIGRATION_STATUS_DEVICE); > + *current_active_state = MIGRATION_STATUS_DEVICE; > + qemu_mutex_lock_iothread(); > + > + return s->state == MIGRATION_STATUS_DEVICE ? 0 : -EINVAL; > +} > + > +/** > * migration_completion: Used by migration_thread when there's not much left. > * The caller 'breaks' the loop when this returns. > * > @@ -1992,6 +2032,11 @@ static void migration_completion(MigrationState *s, int current_active_state, > bool inactivate = !migrate_colo_enabled(); > ret = vm_stop_force_state(RUN_STATE_FINISH_MIGRATE); > if (ret >= 0) { > + ret = migration_maybe_pause(s, ¤t_active_state); > + /* If this worked it will already have inactivated */ > + inactivate &= !migrate_pause_before_device(); > + } > + if (ret >= 0) { > qemu_file_set_rate_limit(s->to_dst_file, INT64_MAX); > ret = qemu_savevm_state_complete_precopy(s->to_dst_file, false, > inactivate); > @@ -2372,6 +2417,7 @@ static void migration_instance_finalize(Object *obj) > > g_free(params->tls_hostname); > g_free(params->tls_creds); > + qemu_sem_destroy(&ms->pause_sem); > } > > static void migration_instance_init(Object *obj) > @@ -2382,6 +2428,7 @@ static void migration_instance_init(Object *obj) > ms->state = MIGRATION_STATUS_NONE; > ms->xbzrle_cache_size = DEFAULT_MIGRATE_CACHE_SIZE; > ms->mbps = -1; > + qemu_sem_init(&ms->pause_sem, 0); > > params->tls_hostname = g_strdup(""); > params->tls_creds = g_strdup(""); > diff --git a/migration/migration.h b/migration/migration.h > index 37feea5453..447e8b3f79 100644 > --- a/migration/migration.h > +++ b/migration/migration.h > @@ -121,6 +121,9 @@ struct MigrationState > /* Flag set once the migration thread called bdrv_inactivate_all */ > bool block_inactive; > > + /* Migration is paused due to pause-before-device */ > + QemuSemaphore pause_sem; > + > /* The semaphore is used to notify COLO thread that failover is finished */ > QemuSemaphore colo_exit_sem; > > -- > 2.13.6 >
* Peter Xu (peterx@redhat.com) wrote: > On Wed, Oct 11, 2017 at 08:13:13PM +0100, Dr. David Alan Gilbert (git) wrote: > > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com> > > > > Wait for a semaphore before completing the migration, > > if the previously added capability was enabled. > > > > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com> > > --- > > migration/migration.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++ > > migration/migration.h | 3 +++ > > 2 files changed, 50 insertions(+) > > > > diff --git a/migration/migration.c b/migration/migration.c > > index e1a87c3d23..b411a7bb63 100644 > > --- a/migration/migration.c > > +++ b/migration/migration.c > > @@ -1967,6 +1967,46 @@ fail: > > } > > > > /** > > + * migration_maybe_pause: Pause if required to by migrate_pause_before_device > > + * called with the iothread locked > > + * Returns: 0 on success > > + */ > > +static int migration_maybe_pause(MigrationState *s, int *current_active_state) > > +{ > > + int ret; > > + if (!migrate_pause_before_device()) { > > + return 0; > > + } > > + ret = bdrv_inactivate_all(); > > My understanding is that the crash was caused by mirrored block device > IO triggered after the inactivation, then... should we do this after > waiting for the semaphore (possibly at [1] below) to make sure the > block jobs are completed? Or did I miss anything? Ah you're right, just confirmed this with kwolf that I got it the wrong way around. I'll fix it. Dave > > + if (ret) { > > + error_report("%s: bdrv_inactivate_all() failed (%d)", > > + __func__, ret); > > + return ret; > > + } > > + > > + s->block_inactive = true; > > + > > + /* Since leaving this state is not atomic with posting the semaphore > > + * it's possible that someone could have issued multiple migrate_continue > > + * and the semaphore is incorrectly positive at this point; > > + * the docs say it's undefined to reinit a semaphore that's already > > + * init'd, so use timedwait to eat up any existing posts. > > + */ > > + while (qemu_sem_timedwait(&s->pause_sem, 1) == 0); > > + > > + qemu_mutex_unlock_iothread(); > > + migrate_set_state(&s->state, *current_active_state, > > + MIGRATION_STATUS_PAUSE_BEFORE_DEVICE); > > + qemu_sem_wait(&s->pause_sem); > > [1] > > > + migrate_set_state(&s->state, MIGRATION_STATUS_PAUSE_BEFORE_DEVICE, > > + MIGRATION_STATUS_DEVICE); > > + *current_active_state = MIGRATION_STATUS_DEVICE; > > + qemu_mutex_lock_iothread(); > > + > > + return s->state == MIGRATION_STATUS_DEVICE ? 0 : -EINVAL; > > +} > > + > > +/** > > * migration_completion: Used by migration_thread when there's not much left. > > * The caller 'breaks' the loop when this returns. > > * > > @@ -1992,6 +2032,11 @@ static void migration_completion(MigrationState *s, int current_active_state, > > bool inactivate = !migrate_colo_enabled(); > > ret = vm_stop_force_state(RUN_STATE_FINISH_MIGRATE); > > if (ret >= 0) { > > + ret = migration_maybe_pause(s, ¤t_active_state); > > + /* If this worked it will already have inactivated */ > > + inactivate &= !migrate_pause_before_device(); > > + } > > + if (ret >= 0) { > > qemu_file_set_rate_limit(s->to_dst_file, INT64_MAX); > > ret = qemu_savevm_state_complete_precopy(s->to_dst_file, false, > > inactivate); > > @@ -2372,6 +2417,7 @@ static void migration_instance_finalize(Object *obj) > > > > g_free(params->tls_hostname); > > g_free(params->tls_creds); > > + qemu_sem_destroy(&ms->pause_sem); > > } > > > > static void migration_instance_init(Object *obj) > > @@ -2382,6 +2428,7 @@ static void migration_instance_init(Object *obj) > > ms->state = MIGRATION_STATUS_NONE; > > ms->xbzrle_cache_size = DEFAULT_MIGRATE_CACHE_SIZE; > > ms->mbps = -1; > > + qemu_sem_init(&ms->pause_sem, 0); > > > > params->tls_hostname = g_strdup(""); > > params->tls_creds = g_strdup(""); > > diff --git a/migration/migration.h b/migration/migration.h > > index 37feea5453..447e8b3f79 100644 > > --- a/migration/migration.h > > +++ b/migration/migration.h > > @@ -121,6 +121,9 @@ struct MigrationState > > /* Flag set once the migration thread called bdrv_inactivate_all */ > > bool block_inactive; > > > > + /* Migration is paused due to pause-before-device */ > > + QemuSemaphore pause_sem; > > + > > /* The semaphore is used to notify COLO thread that failover is finished */ > > QemuSemaphore colo_exit_sem; > > > > -- > > 2.13.6 > > > > -- > Peter Xu -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
diff --git a/migration/migration.c b/migration/migration.c index e1a87c3d23..b411a7bb63 100644 --- a/migration/migration.c +++ b/migration/migration.c @@ -1967,6 +1967,46 @@ fail: } /** + * migration_maybe_pause: Pause if required to by migrate_pause_before_device + * called with the iothread locked + * Returns: 0 on success + */ +static int migration_maybe_pause(MigrationState *s, int *current_active_state) +{ + int ret; + if (!migrate_pause_before_device()) { + return 0; + } + ret = bdrv_inactivate_all(); + if (ret) { + error_report("%s: bdrv_inactivate_all() failed (%d)", + __func__, ret); + return ret; + } + + s->block_inactive = true; + + /* Since leaving this state is not atomic with posting the semaphore + * it's possible that someone could have issued multiple migrate_continue + * and the semaphore is incorrectly positive at this point; + * the docs say it's undefined to reinit a semaphore that's already + * init'd, so use timedwait to eat up any existing posts. + */ + while (qemu_sem_timedwait(&s->pause_sem, 1) == 0); + + qemu_mutex_unlock_iothread(); + migrate_set_state(&s->state, *current_active_state, + MIGRATION_STATUS_PAUSE_BEFORE_DEVICE); + qemu_sem_wait(&s->pause_sem); + migrate_set_state(&s->state, MIGRATION_STATUS_PAUSE_BEFORE_DEVICE, + MIGRATION_STATUS_DEVICE); + *current_active_state = MIGRATION_STATUS_DEVICE; + qemu_mutex_lock_iothread(); + + return s->state == MIGRATION_STATUS_DEVICE ? 0 : -EINVAL; +} + +/** * migration_completion: Used by migration_thread when there's not much left. * The caller 'breaks' the loop when this returns. * @@ -1992,6 +2032,11 @@ static void migration_completion(MigrationState *s, int current_active_state, bool inactivate = !migrate_colo_enabled(); ret = vm_stop_force_state(RUN_STATE_FINISH_MIGRATE); if (ret >= 0) { + ret = migration_maybe_pause(s, ¤t_active_state); + /* If this worked it will already have inactivated */ + inactivate &= !migrate_pause_before_device(); + } + if (ret >= 0) { qemu_file_set_rate_limit(s->to_dst_file, INT64_MAX); ret = qemu_savevm_state_complete_precopy(s->to_dst_file, false, inactivate); @@ -2372,6 +2417,7 @@ static void migration_instance_finalize(Object *obj) g_free(params->tls_hostname); g_free(params->tls_creds); + qemu_sem_destroy(&ms->pause_sem); } static void migration_instance_init(Object *obj) @@ -2382,6 +2428,7 @@ static void migration_instance_init(Object *obj) ms->state = MIGRATION_STATUS_NONE; ms->xbzrle_cache_size = DEFAULT_MIGRATE_CACHE_SIZE; ms->mbps = -1; + qemu_sem_init(&ms->pause_sem, 0); params->tls_hostname = g_strdup(""); params->tls_creds = g_strdup(""); diff --git a/migration/migration.h b/migration/migration.h index 37feea5453..447e8b3f79 100644 --- a/migration/migration.h +++ b/migration/migration.h @@ -121,6 +121,9 @@ struct MigrationState /* Flag set once the migration thread called bdrv_inactivate_all */ bool block_inactive; + /* Migration is paused due to pause-before-device */ + QemuSemaphore pause_sem; + /* The semaphore is used to notify COLO thread that failover is finished */ QemuSemaphore colo_exit_sem;