changes that went into kernel v5.0.
* d6a51a97c0b2 ("blk-mq: replace and kill blk_mq_request_issue_directly") # v5.0.
* 5b7a6f128aad ("blk-mq: issue directly with bypass 'false' in blk_mq_sched_insert_requests") # v5.0.
* 7f556a44e61d ("blk-mq: refactor the code of issue request directly") # v5.0.
Fixes: 7f556a44e61d ("blk-mq: refactor the code of issue request directly") # v5.0.
-	 * hctx_lock is needed before checking quiesced flag.
+	 * RCU or SRCU read lock is needed before checking quiesced flag.
+	 * and avoid driver to try to dispatch again.
-	 *.queue_rq() to the hardware dispatch list.
-			 * request is direct-issued successfully.