iov_iter_reexpand
iov_iter_reexpand(from, iov_iter_count(from) + shorted);
iov_iter_reexpand(to, iov_iter_count(to) + shorted);
iov_iter_reexpand(iter, orig_count);
iov_iter_reexpand(iter, iov_iter_count(iter) + shortened);
iov_iter_reexpand(dio->submit.iter, orig_count - copied);
iov_iter_reexpand(from, count);
iov_iter_reexpand(i, iov_iter_count(i) + shorted);