This makes the assignment typesafe. It prepares
changing io_kiocb_to_cmd() in the next commit.
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Link: https://lore.kernel.org/r/8da6e9d12cf95ad4bc73274406d12bca7aabf72e.1660201408.git.metze@samba.orgSigned-off-by: Jens Axboe <axboe@kernel.dk>