diff --git a/include/linux/page_ext.h b/include/linux/page_ext.h
new file mode 100644
index 0000000..2ccc8b4
--- /dev/null
+++ b/include/linux/page_ext.h
@@ -0,0 +1,59 @@
+#ifndef __LINUX_PAGE_EXT_H
+#define __LINUX_PAGE_EXT_H
+
+struct pglist_data;
+struct page_ext_operations {
+	bool (*need)(void);
+	void (*init)(void);
+};
+
+#ifdef CONFIG_PAGE_EXTENSION
+
+/*
+ * Page Extension can be considered as an extended mem_map.
+ * A page_ext page is associated with every page descriptor. The
+ * page_ext helps us add more information about the page.
+ * All page_ext are allocated at boot or memory hotplug event,
+ * then the page_ext for pfn always exists.
+ */
+struct page_ext {
+	unsigned long flags;
+};
+
+extern void pgdat_page_ext_init(struct pglist_data *pgdat);
+
+#ifdef CONFIG_SPARSEMEM
+static inline void page_ext_init_flatmem(void)
+{
+}
+extern void page_ext_init(void);
+#else
+extern void page_ext_init_flatmem(void);
+static inline void page_ext_init(void)
+{
+}
+#endif
+
+struct page_ext *lookup_page_ext(struct page *page);
+
+#else /* !CONFIG_PAGE_EXTENSION */
+struct page_ext;
+
+static inline void pgdat_page_ext_init(struct pglist_data *pgdat)
+{
+}
+
+static inline struct page_ext *lookup_page_ext(struct page *page)
+{
+	return NULL;
+}
+
+static inline void page_ext_init(void)
+{
+}
+
+static inline void page_ext_init_flatmem(void)
+{
+}
+#endif /* CONFIG_PAGE_EXTENSION */
+#endif /* __LINUX_PAGE_EXT_H */