+ if (blk_mq_can_use_cached_rq(rq, plug, bio))
+ goto done;
+ percpu_ref_get(&q->q_usage_counter);
+ } else {
+ if (unlikely(bio_queue_enter(bio)))
+ return;
+ if (!bio_integrity_prep(bio))
+ goto fail;
+ }
+
+ rq = blk_mq_get_new_requests(q, plug, bio, nr_segs);
+ if (unlikely(!rq)) {
+fail:
+ blk_queue_exit(q);
+ return;