ublk: avoid redundant io->cmd in ublk_queue_cmd_list()

ublk_queue_cmd_list() loads io->cmd twice. The intervening stores
prevent the compiler from combining the loads. Since struct ublk_io *io
is only used to compute io->cmd, replace the variable with io->cmd.

Signed-off-by: Caleb Sander Mateos <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>

Author: calebsander

drivers/block/ublk_drv.c

@@ -1301,12 +1301,12 @@ static void ublk_cmd_list_tw_cb(struct io_uring_cmd *cmd,
 static void ublk_queue_cmd_list(struct ublk_queue *ubq, struct rq_list *l)
 {
 	struct request *rq = rq_list_peek(l);
-	struct ublk_io *io = &ubq->ios[rq->tag];
-	struct ublk_uring_cmd_pdu *pdu = ublk_get_uring_cmd_pdu(io->cmd);
+	struct io_uring_cmd *cmd = ubq->ios[rq->tag].cmd;
+	struct ublk_uring_cmd_pdu *pdu = ublk_get_uring_cmd_pdu(cmd);
 
 	pdu->req_list = rq;
 	rq_list_init(l);
-	io_uring_cmd_complete_in_task(io->cmd, ublk_cmd_list_tw_cb);
+	io_uring_cmd_complete_in_task(cmd, ublk_cmd_list_tw_cb);
 }
 
 static enum blk_eh_timer_return ublk_timeout(struct request *rq)