blk-cgroup: don't quiesce the queue on policy activate/deactivate

There's no potential harm in quiescing the queue, but it also doesn't
buy us anything. And we can't run the queue async for policy
deactivate, since we could be in the path of tearing the queue down.
If we schedule an async run of the queue at that time, we're racing
with queue teardown AFTER having we've already torn most of it down.
Reported-by: NOmar Sandoval <osandov@fb.com>
Fixes: 4d199c6f ("blk-cgroup: ensure that we clear the stop bit on quiesced queues")
Tested-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

block/blk-cgroup.c

@@ -1223,10 +1223,9 @@ int blkcg_activate_policy(struct request_queue *q,
 	if (blkcg_policy_enabled(q, pol))
 		return 0;
 
-	if (q->mq_ops) {
+	if (q->mq_ops)
 		blk_mq_freeze_queue(q);
-		blk_mq_quiesce_queue(q);
-	} else
+	else
 		blk_queue_bypass_start(q);
 pd_prealloc:
 	if (!pd_prealloc) {
@@ -1265,10 +1264,9 @@ int blkcg_activate_policy(struct request_queue *q,
 
 	spin_unlock_irq(q->queue_lock);
 out_bypass_end:
-	if (q->mq_ops) {
+	if (q->mq_ops)
 		blk_mq_unfreeze_queue(q);
-		blk_mq_start_stopped_hw_queues(q, true);
-	} else
+	else
 		blk_queue_bypass_end(q);
 	if (pd_prealloc)
 		pol->pd_free_fn(pd_prealloc);
@@ -1292,10 +1290,9 @@ void blkcg_deactivate_policy(struct request_queue *q,
 	if (!blkcg_policy_enabled(q, pol))
 		return;
 
-	if (q->mq_ops) {
+	if (q->mq_ops)
 		blk_mq_freeze_queue(q);
-		blk_mq_quiesce_queue(q);
-	} else
+	else
 		blk_queue_bypass_start(q);
 
 	spin_lock_irq(q->queue_lock);
@@ -1318,10 +1315,9 @@ void blkcg_deactivate_policy(struct request_queue *q,
 
 	spin_unlock_irq(q->queue_lock);
 
-	if (q->mq_ops) {
+	if (q->mq_ops)
 		blk_mq_unfreeze_queue(q);
-		blk_mq_start_stopped_hw_queues(q, true);
-	} else
+	else
 		blk_queue_bypass_end(q);
 }
 EXPORT_SYMBOL_GPL(blkcg_deactivate_policy);