1 files changed, 50 insertions, 13 deletions

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index d25bd224d370..d6661de56f30 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -26,8 +26,18 @@
  */
 struct anon_vma {
 	spinlock_t lock;	/* Serialize access to vma list */
-#ifdef CONFIG_KSM
-	atomic_t ksm_refcount;
+	struct anon_vma *root;	/* Root of this anon_vma tree */
+#if defined(CONFIG_KSM) || defined(CONFIG_MIGRATION)
+
+	/*
+	 * The external_refcount is taken by either KSM or page migration
+	 * to take a reference to an anon_vma when there is no
+	 * guarantee that the vma of page tables will exist for
+	 * the duration of the operation. A caller that takes
+	 * the reference is responsible for clearing up the
+	 * anon_vma if they are the last user on release
+	 */
+	atomic_t external_refcount;
 #endif
 	/*
 	 * NOTE: the LSB of the head.next is set by
@@ -61,25 +71,40 @@ struct anon_vma_chain {
 };
 
 #ifdef CONFIG_MMU
-#ifdef CONFIG_KSM
-static inline void ksm_refcount_init(struct anon_vma *anon_vma)
+#if defined(CONFIG_KSM) || defined(CONFIG_MIGRATION)
+static inline void anonvma_external_refcount_init(struct anon_vma *anon_vma)
+{
+	atomic_set(&anon_vma->external_refcount, 0);
+}
+
+static inline int anonvma_external_refcount(struct anon_vma *anon_vma)
 {
-	atomic_set(&anon_vma->ksm_refcount, 0);
+	return atomic_read(&anon_vma->external_refcount);
 }
 
-static inline int ksm_refcount(struct anon_vma *anon_vma)
+static inline void get_anon_vma(struct anon_vma *anon_vma)
 {
-	return atomic_read(&anon_vma->ksm_refcount);
+	atomic_inc(&anon_vma->external_refcount);
 }
+
+void drop_anon_vma(struct anon_vma *);
 #else
-static inline void ksm_refcount_init(struct anon_vma *anon_vma)
+static inline void anonvma_external_refcount_init(struct anon_vma *anon_vma)
 {
 }
 
-static inline int ksm_refcount(struct anon_vma *anon_vma)
+static inline int anonvma_external_refcount(struct anon_vma *anon_vma)
 {
 	return 0;
 }
+
+static inline void get_anon_vma(struct anon_vma *anon_vma)
+{
+}
+
+static inline void drop_anon_vma(struct anon_vma *anon_vma)
+{
+}
 #endif /* CONFIG_KSM */
 
 static inline struct anon_vma *page_anon_vma(struct page *page)
@@ -90,18 +115,28 @@ static inline struct anon_vma *page_anon_vma(struct page *page)
 	return page_rmapping(page);
 }
 
-static inline void anon_vma_lock(struct vm_area_struct *vma)
+static inline void vma_lock_anon_vma(struct vm_area_struct *vma)
 {
 	struct anon_vma *anon_vma = vma->anon_vma;
 	if (anon_vma)
-		spin_lock(&anon_vma->lock);
+		spin_lock(&anon_vma->root->lock);
 }
 
-static inline void anon_vma_unlock(struct vm_area_struct *vma)
+static inline void vma_unlock_anon_vma(struct vm_area_struct *vma)
 {
 	struct anon_vma *anon_vma = vma->anon_vma;
 	if (anon_vma)
-		spin_unlock(&anon_vma->lock);
+		spin_unlock(&anon_vma->root->lock);
+}
+
+static inline void anon_vma_lock(struct anon_vma *anon_vma)
+{
+	spin_lock(&anon_vma->root->lock);
+}
+
+static inline void anon_vma_unlock(struct anon_vma *anon_vma)
+{
+	spin_unlock(&anon_vma->root->lock);
 }
 
 /*
@@ -127,6 +162,8 @@ static inline void anon_vma_merge(struct vm_area_struct *vma,
  */
 void page_move_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
 void page_add_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
+void do_page_add_anon_rmap(struct page *, struct vm_area_struct *,
+			   unsigned long, int);
 void page_add_new_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
 void page_add_file_rmap(struct page *);
 void page_remove_rmap(struct page *);