diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 0b4913a..980094a 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -26,6 +26,9 @@
  */
 struct anon_vma {
 	spinlock_t lock;	/* Serialize access to vma list */
+#ifdef CONFIG_KSM
+	atomic_t ksm_refcount;
+#endif
 	/*
 	 * NOTE: the LSB of the head.next is set by
 	 * mm_take_all_locks() _after_ taking the above lock. So the
@@ -38,6 +41,26 @@
 };
 
 #ifdef CONFIG_MMU
+#ifdef CONFIG_KSM
+static inline void ksm_refcount_init(struct anon_vma *anon_vma)
+{
+	atomic_set(&anon_vma->ksm_refcount, 0);
+}
+
+static inline int ksm_refcount(struct anon_vma *anon_vma)
+{
+	return atomic_read(&anon_vma->ksm_refcount);
+}
+#else
+static inline void ksm_refcount_init(struct anon_vma *anon_vma)
+{
+}
+
+static inline int ksm_refcount(struct anon_vma *anon_vma)
+{
+	return 0;
+}
+#endif /* CONFIG_KSM */
 
 static inline struct anon_vma *page_anon_vma(struct page *page)
 {
@@ -70,6 +93,7 @@
 void anon_vma_unlink(struct vm_area_struct *);
 void anon_vma_link(struct vm_area_struct *);
 void __anon_vma_link(struct vm_area_struct *);
+void anon_vma_free(struct anon_vma *);
 
 /*
  * rmap interfaces called when adding or removing pte of page