+/* Disk used for filesystem. */
+extern struct disk *filesys_disk;
+
+/* The free map file, opened by filesys_init() and never
+ closed. */
+extern struct file *free_map_file;
+
+void filesys_init (bool format);
+void filesys_done (void);
+bool filesys_create (const char *name, off_t initial_size);