xdr_process_buf
extern int xdr_process_buf(const struct xdr_buf *buf, unsigned int offset, unsigned int len, int (*actor)(struct scatterlist *, void *), void *data);
err = xdr_process_buf(body, body_offset, body->len - body_offset,
err = xdr_process_buf(buf, offset, cbcbytes, encryptor, &desc);
err = xdr_process_buf(buf, 0, cbcbytes, decryptor, &desc);
err = xdr_process_buf(body, body_offset, body->len - body_offset,
EXPORT_SYMBOL_GPL(xdr_process_buf);