[1/2] migration: move bdrv_invalidate_cache_all of of coroutine context

There is a possibility to hit an assert in qcow2_get_specific_info that
s->qcow_version is undefined. This happens when VM in starting from
suspended state, i.e. it processes incoming migration, and in the same
time 'info block' is called.

The problem is that qcow2_invalidate_cache() closes the image and
memset()s BDRVQcowState in the middle.

The patch moves processing of bdrv_invalidate_cache_all out of
coroutine context for standard migration to avoid that.

Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Juan Quintela <quintela@redhat.com>
CC: Amit Shah <amit.shah@redhat.com>
---
 migration/migration.c | 89 ++++++++++++++++++++++++++++-----------------------
 1 file changed, 49 insertions(+), 40 deletions(-)

On Fri, 02/12 09:39, Denis V. Lunev wrote:
> There is a possibility to hit an assert in qcow2_get_specific_info that
> s->qcow_version is undefined. This happens when VM in starting from
> suspended state, i.e. it processes incoming migration, and in the same
> time 'info block' is called.
> 
> The problem is that qcow2_invalidate_cache() closes the image and
> memset()s BDRVQcowState in the middle.
> 
> The patch moves processing of bdrv_invalidate_cache_all out of
> coroutine context for standard migration to avoid that.
> 
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> CC: Paolo Bonzini <pbonzini@redhat.com>
> CC: Juan Quintela <quintela@redhat.com>
> CC: Amit Shah <amit.shah@redhat.com>
> ---
>  migration/migration.c | 89 ++++++++++++++++++++++++++++-----------------------
>  1 file changed, 49 insertions(+), 40 deletions(-)
> 
> diff --git a/migration/migration.c b/migration/migration.c
> index a64cfcd..1f8535e 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -323,13 +323,59 @@ void qemu_start_incoming_migration(const char *uri, Error **errp)
>      }
>  }
>  
> +static void process_incoming_migration_bh(void *opaque)
> +{
> +    Error *local_err = NULL;
> +    MigrationIncomingState *mis = opaque;
> +
> +    /* Make sure all file formats flush their mutable metadata */
> +    bdrv_invalidate_cache_all(&local_err);
> +    if (local_err) {
> +        migrate_set_state(&mis->state, MIGRATION_STATUS_ACTIVE,
> +                          MIGRATION_STATUS_FAILED);
> +        error_report_err(local_err);
> +        migrate_decompress_threads_join();
> +        exit(EXIT_FAILURE);
> +    }
> +
> +    /*
> +     * This must happen after all error conditions are dealt with and
> +     * we're sure the VM is going to be running on this host.
> +     */
> +    qemu_announce_self();
> +
> +    /* If global state section was not received or we are in running
> +       state, we need to obey autostart. Any other state is set with
> +       runstate_set. */
> +
> +    if (!global_state_received() ||
> +        global_state_get_runstate() == RUN_STATE_RUNNING) {
> +        if (autostart) {
> +            vm_start();
> +        } else {
> +            runstate_set(RUN_STATE_PAUSED);
> +        }
> +    } else {
> +        runstate_set(global_state_get_runstate());
> +    }
> +    migrate_decompress_threads_join();
> +    /*
> +     * This must happen after any state changes since as soon as an external
> +     * observer sees this event they might start to prod at the VM assuming
> +     * it's ready to use.
> +     */
> +    migrate_set_state(&mis->state, MIGRATION_STATUS_ACTIVE,
> +                      MIGRATION_STATUS_COMPLETED);
> +    migration_incoming_state_destroy();
> +}
> +
>  static void process_incoming_migration_co(void *opaque)
>  {
>      QEMUFile *f = opaque;
> -    Error *local_err = NULL;
>      MigrationIncomingState *mis;
>      PostcopyState ps;
>      int ret;
> +    QEMUBH *bh;
>  
>      mis = migration_incoming_state_new(f);
>      postcopy_state_set(POSTCOPY_INCOMING_NONE);
> @@ -369,45 +415,8 @@ static void process_incoming_migration_co(void *opaque)
>          exit(EXIT_FAILURE);
>      }
>  
> -    /* Make sure all file formats flush their mutable metadata */
> -    bdrv_invalidate_cache_all(&local_err);
> -    if (local_err) {
> -        migrate_set_state(&mis->state, MIGRATION_STATUS_ACTIVE,
> -                          MIGRATION_STATUS_FAILED);
> -        error_report_err(local_err);
> -        migrate_decompress_threads_join();
> -        exit(EXIT_FAILURE);
> -    }
> -
> -    /*
> -     * This must happen after all error conditions are dealt with and
> -     * we're sure the VM is going to be running on this host.
> -     */
> -    qemu_announce_self();
> -
> -    /* If global state section was not received or we are in running
> -       state, we need to obey autostart. Any other state is set with
> -       runstate_set. */
> -
> -    if (!global_state_received() ||
> -        global_state_get_runstate() == RUN_STATE_RUNNING) {
> -        if (autostart) {
> -            vm_start();
> -        } else {
> -            runstate_set(RUN_STATE_PAUSED);
> -        }
> -    } else {
> -        runstate_set(global_state_get_runstate());
> -    }
> -    migrate_decompress_threads_join();
> -    /*
> -     * This must happen after any state changes since as soon as an external
> -     * observer sees this event they might start to prod at the VM assuming
> -     * it's ready to use.
> -     */
> -    migrate_set_state(&mis->state, MIGRATION_STATUS_ACTIVE,
> -                      MIGRATION_STATUS_COMPLETED);
> -    migration_incoming_state_destroy();
> +    bh = qemu_bh_new(process_incoming_migration_bh, mis);

Don't you need to call qemu_bh_delete somewhere? (Also applies to the other
patch)

Fam

> +    qemu_bh_schedule(bh);
>  }
>  
>  void process_incoming_migration(QEMUFile *f)
> -- 
> 2.1.4
> 
>