ublk: don't access ublk_queue in ublk_register_io_buf()

For ublk servers with many ublk queues, accessing the ublk_queue in
ublk_register_io_buf() is a frequent cache miss. Get the flags from the
ublk_device instead, which is accessed earlier in
ublk_ch_uring_cmd_local().

Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: calebsander

drivers/block/ublk_drv.c

@@ -2133,7 +2133,7 @@ static int ublk_register_io_buf(struct io_uring_cmd *cmd,
 	struct request *req;
 	int ret;
 
-	if (!ublk_support_zero_copy(ubq))
+	if (!ublk_dev_support_zero_copy(ub))
 		return -EINVAL;
 
 	req = __ublk_check_and_get_req(ub, ubq, io, 0);