[PATCH 5/5] ublk: store req in ublk_uring_cmd_pdu for ublk_cmd_tw_cb()

[Caleb Sander Mateos <csander@purestorage.com>]

Pass struct request *rq to ublk_cmd_tw_cb() through ublk_uring_cmd_pdu,
mirroring how it works for ublk_cmd_list_tw_cb(). This saves some
pointer dereferences, as well as the bounds check in blk_mq_tag_to_rq().

Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
---
 drivers/block/ublk_drv.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index 23250471562a..466a23b89379 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -87,11 +87,14 @@ struct ublk_uring_cmd_pdu {
 	 *
 	 * It should have been stored to request payload, but we do want
 	 * to avoid extra pre-allocation, and uring_cmd payload is always
 	 * free for us
 	 */
-	struct request *req_list;
+	union {
+		struct request *req;
+		struct request *req_list;
+	};
 
 	/*
 	 * The following two are valid in this cmd whole lifetime, and
 	 * setup in ublk uring_cmd handler
 	 */
@@ -1266,22 +1269,21 @@ static void ublk_dispatch_req(struct ublk_queue *ubq,
 static void ublk_cmd_tw_cb(struct io_uring_cmd *cmd,
 			   unsigned int issue_flags)
 {
 	struct ublk_uring_cmd_pdu *pdu = ublk_get_uring_cmd_pdu(cmd);
 	struct ublk_queue *ubq = pdu->ubq;
-	int tag = pdu->tag;
-	struct request *req = blk_mq_tag_to_rq(
-		ubq->dev->tag_set.tags[ubq->q_id], tag);
 
-	ublk_dispatch_req(ubq, req, issue_flags);
+	ublk_dispatch_req(ubq, pdu->req, issue_flags);
 }
 
 static void ublk_queue_cmd(struct ublk_queue *ubq, struct request *rq)
 {
-	struct ublk_io *io = &ubq->ios[rq->tag];
+	struct io_uring_cmd *cmd = ubq->ios[rq->tag].cmd;
+	struct ublk_uring_cmd_pdu *pdu = ublk_get_uring_cmd_pdu(cmd);
 
-	io_uring_cmd_complete_in_task(io->cmd, ublk_cmd_tw_cb);
+	pdu->req = rq;
+	io_uring_cmd_complete_in_task(cmd, ublk_cmd_tw_cb);
 }
 
 static void ublk_cmd_list_tw_cb(struct io_uring_cmd *cmd,
 		unsigned int issue_flags)
 {
-- 
2.45.2