unsigned long nr_segs, size_t len, loff_t *ppos, iov_fn_t fn);
ssize_t do_loop_readv_writev(struct file *filp, struct iovec *iov,
unsigned long nr_segs, loff_t *ppos, io_fn_t fn);
+ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos, size_t count,
+ loff_t max);