size_t num_pages, loff_t pos, size_t write_bytes,
struct extent_state **cached);
int btrfs_fdatawrite_range(struct inode *inode, loff_t start, loff_t end);
-ssize_t btrfs_copy_file_range(struct file *file_in, loff_t pos_in,
- struct file *file_out, loff_t pos_out,
- size_t len, unsigned int flags);
int btrfs_clone_file_range(struct file *file_in, loff_t pos_in,
struct file *file_out, loff_t pos_out, u64 len);