blk-mq: place trace_block_getrq() in correct place

mainline inclusion
from mainline-4.20-rc1
commit d6f1dda27251909a27b8d8aacb498628a1047978
category: bugfix
bugzilla: 9637
CVE: NA
---------------------------

trace_block_getrq() is to indicate a request struct has been allocated
for queue, so put it in right place.
Reviewed-by: NJianchao Wang <jianchao.w.wang@oracle.com>
Signed-off-by: NXiaoguang Wang <xiaoguang.wang@linux.alibaba.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
Signed-off-by: NYufen Yu <yuyufen@huawei.com>
Reviewed-by: NHou Tao <houtao1@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

block/blk-mq.c

@@ -1834,8 +1834,6 @@ 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);
@@ -1844,6 +1842,8 @@ 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);