- int (*read)(const char *filename, void *buf, int offset, int len);
- int (*write)(const char *filename, void *buf, int offset, int len);
+ int (*exists)(const char *filename);
+ int (*size)(const char *filename, loff_t *size);
+ int (*read)(const char *filename, void *buf, loff_t offset,
+ loff_t len, loff_t *actread);
+ int (*write)(const char *filename, void *buf, loff_t offset,
+ loff_t len, loff_t *actwrite);