blockjob: add set_speed to BlockJobDriver

We are going to use async block-copy call in backup, so we'll need to
passthrough setting backup speed to block-copy call.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20210116214705.822267-9-vsementsov@virtuozzo.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>

blockjob.c

@@ -256,6 +256,7 @@ static bool job_timer_pending(Job *job)
 
 void block_job_set_speed(BlockJob *job, int64_t speed, Error **errp)
 {
+    const BlockJobDriver *drv = block_job_driver(job);
     int64_t old_speed = job->speed;
 
     if (job_apply_verb(&job->job, JOB_VERB_SET_SPEED, errp)) {
@@ -270,6 +271,11 @@ void block_job_set_speed(BlockJob *job, int64_t speed, Error **errp)
     ratelimit_set_speed(&job->limit, speed, BLOCK_JOB_SLICE_TIME);
 
     job->speed = speed;
+
+    if (drv->set_speed) {
+        drv->set_speed(job, speed);
+    }
+
     if (speed && speed <= old_speed) {
         return;
     }

include/block/blockjob_int.h

@@ -52,6 +52,8 @@ struct BlockJobDriver {
      * besides job->blk to the new AioContext.
      */
     void (*attached_aio_context)(BlockJob *job, AioContext *new_context);
+
+    void (*set_speed)(BlockJob *job, int64_t speed);
 };
 
 /**