extern int vmtruncate_range(struct inode * inode, loff_t offset, loff_t end);
int truncate_inode_page(struct address_space *mapping, struct page *page);
extern int vmtruncate_range(struct inode * inode, loff_t offset, loff_t end);
int truncate_inode_page(struct address_space *mapping, struct page *page);