[RFC PATCH 2/5 COMPILE TESTED] nvme-rdma: reduce blk_rq_nr_phys_segments calls

[Chaitanya Kulkarni]

In the fast path blk_rq_nr_phys_segments() is called twice for RDMA
fabric. The function blk_rq_nr_phys_segments() adds a if check for
special payload. The same check gets repeated number of times we call
the function in the fast path.

In order to minimize repetitive check in the fast path this patch
reduces the number of calls to one and adjust the code in submission
path.

Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni at wdc.com>
---
 drivers/nvme/host/rdma.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/nvme/host/rdma.c b/drivers/nvme/host/rdma.c
index 13506a87a444..736e5741dbdc 100644
--- a/drivers/nvme/host/rdma.c
+++ b/drivers/nvme/host/rdma.c
@@ -1444,6 +1444,7 @@ static int nvme_rdma_map_data(struct nvme_rdma_queue *queue,
 		struct request *rq, struct nvme_command *c)
 {
 	struct nvme_rdma_request *req = blk_mq_rq_to_pdu(rq);
+	unsigned short nseg = blk_rq_nr_phys_segments(rq);
 	struct nvme_rdma_device *dev = queue->device;
 	struct ib_device *ibdev = dev->dev;
 	int pi_count = 0;
@@ -1454,13 +1455,12 @@ static int nvme_rdma_map_data(struct nvme_rdma_queue *queue,
 
 	c->common.flags |= NVME_CMD_SGL_METABUF;
 
-	if (!blk_rq_nr_phys_segments(rq))
+	if (!nseg)
 		return nvme_rdma_set_sg_null(c);
 
 	req->data_sgl.sg_table.sgl = (struct scatterlist *)(req + 1);
-	ret = sg_alloc_table_chained(&req->data_sgl.sg_table,
-			blk_rq_nr_phys_segments(rq), req->data_sgl.sg_table.sgl,
-			NVME_INLINE_SG_CNT);
+	ret = sg_alloc_table_chained(&req->data_sgl.sg_table, nseg,
+			req->data_sgl.sg_table.sgl, NVME_INLINE_SG_CNT);
 	if (ret)
 		return -ENOMEM;
 
-- 
2.22.0