off_t file_read (struct file *, void *, off_t);
off_t file_write (struct file *, const void *, off_t);
off_t file_length (struct file *);
off_t file_read (struct file *, void *, off_t);
off_t file_write (struct file *, const void *, off_t);
off_t file_length (struct file *);