iov_iter_ubuf
iov_iter_ubuf(&iter, rq_data_dir(rq), ubuf, bytes);
iov_iter_ubuf(&iter, ITER_SOURCE, (void __user *)user_data, size);
iov_iter_ubuf(&iter, ITER_DEST, (void __user *)addr, length);
iov_iter_ubuf(&iter, ITER_DEST, buf, len);
iov_iter_ubuf(&iter, ITER_SOURCE, (void __user *)buf, len);
iov_iter_ubuf(&kmsg->msg.msg_iter, ITER_DEST, sel.addr, len);
iov_iter_ubuf(i, rw, buf, len);
iov_iter_ubuf(&iter, READ, data.ubuf, bufsize);
iov_iter_ubuf(&opt->iter_out, ITER_DEST, optval.user, koptlen);
iov_iter_ubuf(&opt->iter_in, ITER_SOURCE, optval.user,