blk-mq: reimplement blk_mq_hw_queue_mapped

Now the actual meaning of queue mapped is that if there is any online
CPU mapped to this hctx, so implement blk_mq_hw_queue_mapped() in this
way.

Cc: Stefan Haberland <sth@linux.vnet.ibm.com>
Tested-by: NChristian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NSagi Grimberg <sagi@grimberg.me>
Signed-off-by: NMing Lei <ming.lei@redhat.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

block/blk-mq.h

@@ -181,7 +181,7 @@ static inline bool blk_mq_hctx_stopped(struct blk_mq_hw_ctx *hctx)
 
 static inline bool blk_mq_hw_queue_mapped(struct blk_mq_hw_ctx *hctx)
 {
-	return hctx->nr_ctx && hctx->tags;
+	return cpumask_first_and(hctx->cpumask, cpu_online_mask) < nr_cpu_ids;
 }
 
 void blk_mq_in_flight(struct request_queue *q, struct hd_struct *part,