* | `- direct node (5 + N => 5 + 2N - 1)
* `- double indirect node (5 + 2N)
* `- indirect node (6 + 2N)
- * `- direct node (x(N + 1))
+ * `- direct node
+ * ......
+ * `- indirect node ((6 + 2N) + x(N + 1))
+ * `- direct node
+ * ......
+ * `- indirect node ((6 + 2N) + (N - 1)(N + 1))
+ * `- direct node
*/
static inline bool IS_DNODE(struct page *node_page)
{