blk-mq: place trace_block_getrq() in correct place

trace_block_getrq() is to indicate a request struct has been allocated
for queue, so put it in right place.
Reviewed-by: Jianchao Wang <jianchao.w.wang@oracle.com>
Signed-off-by: Xiaoguang Wang <xiaoguang.wang@linux.alibaba.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-mq.c

@@ -1850,8 +1850,6 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
 
 	rq_qos_throttle(q, bio, NULL);
 
-	trace_block_getrq(q, bio, bio->bi_opf);
-
 	rq = blk_mq_get_request(q, bio, bio->bi_opf, &data);
 	if (unlikely(!rq)) {
 		rq_qos_cleanup(q, bio);
@@ -1860,6 +1858,8 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
 		return BLK_QC_T_NONE;
 	}
 
+	trace_block_getrq(q, bio, bio->bi_opf);
+
 	rq_qos_track(q, rq, bio);
 
 	cookie = request_to_qc_t(data.hctx, rq);