block: add a rq_dma_dir helper

fix #29327388

commit 9d9de535f385a8b3ba0e88ca0abf386c5704bbfc upstream

In a lot of places we want to know the DMA direction for a given
struct request.  Add a little helper to make it a littler easier.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NKeith Busch <keith.busch@intel.com>
Reviewed-by: NSagi Grimberg <sagi@grimberg.me>
Reviewed-by: NChaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: NBaolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: NJoseph Qi <joseph.qi@linux.alibaba.com>

include/linux/blkdev.h

@@ -791,6 +791,9 @@ static inline bool blk_account_rq(struct request *rq)
 
 #define rq_data_dir(rq)		(op_is_write(req_op(rq)) ? WRITE : READ)
 
+#define rq_dma_dir(rq) \
+	(op_is_write(req_op(rq)) ? DMA_TO_DEVICE : DMA_FROM_DEVICE)
+
 /*
  * Driver can handle struct request, if it either has an old style
  * request_fn defined, or is blk-mq based.