We can avoid a function call virtblk_map_data() in the fast path if
block layer request has no physical segments by moving the call
blk_rq_nr_phys_segments() from virtblk_map_data() to virtio_queue_rq().
Signed-off-by: Chaitanya Kulkarni <kch@xxxxxxxxxx>
---
drivers/block/virtio_blk.c | 15 +++++++--------
1 file changed, 7 insertions(+), 8 deletions(-)
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index d038800474c2..74c3a48cd1e5 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -178,9 +178,6 @@ static int virtblk_map_data(struct blk_mq_hw_ctx *hctx, struct request *req,
{
int err;
- if (!blk_rq_nr_phys_segments(req))
- return 0;
-
vbr->sg_table.sgl = vbr->sg;
err = sg_alloc_table_chained(&vbr->sg_table,
blk_rq_nr_phys_segments(req),
@@ -303,7 +300,7 @@ static blk_status_t virtio_queue_rq(struct blk_mq_hw_ctx *hctx,
struct request *req = bd->rq;
struct virtblk_req *vbr = blk_mq_rq_to_pdu(req);
unsigned long flags;
- int num;
+ int num = 0;
int qid = hctx->queue_num;
bool notify = false;
blk_status_t status;
@@ -315,10 +312,12 @@ static blk_status_t virtio_queue_rq(struct blk_mq_hw_ctx *hctx,
blk_mq_start_request(req);
- num = virtblk_map_data(hctx, req, vbr);
- if (unlikely(num < 0)) {
- virtblk_cleanup_cmd(req);
- return BLK_STS_RESOURCE;
+ if (blk_rq_nr_phys_segments(req)) {
+ num = virtblk_map_data(hctx, req, vbr);
+ if (unlikely(num < 0)) {
+ virtblk_cleanup_cmd(req);
+ return BLK_STS_RESOURCE;
+ }
}
spin_lock_irqsave(&vblk->vqs[qid].lock, flags);
--
2.29.0
