int kernel_sendpage(struct socket *sock, struct page *page, int offset,
size_t size, int flags);
int kernel_sendpage_locked(struct sock *sk, struct page *page, int offset,
int kernel_sendpage(struct socket *sock, struct page *page, int offset,
size_t size, int flags);
int kernel_sendpage_locked(struct sock *sk, struct page *page, int offset,