netfs_extract_user_iter
ret = netfs_extract_user_iter(iter, rreq->len, &rreq->buffer.iter, 0);
n = netfs_extract_user_iter(iter, len, &wreq->buffer.iter, 0);
EXPORT_SYMBOL_GPL(netfs_extract_user_iter);
ssize_t netfs_extract_user_iter(struct iov_iter *orig, size_t orig_len,