From 3a69f2fb730ada06764417f9c68e95311b955a84 Mon Sep 17 00:00:00 2001
From: Hugh Dickins <hughd@google.com>
Date: Fri, 22 Feb 2013 16:36:06 -0800
Subject: [PATCH] --- yaml --- r: 356629 b: refs/heads/master c:
 bc56620b493496b8a6962080b644ccc537f4d526 h: refs/heads/master i:   356627:
 1b71dea94b6c77dc5ea22436584d46e554a42675 v: v3

---
 [refs]         |  2 +-
 trunk/mm/ksm.c | 26 ++++++++++++++------------
 2 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/[refs] b/[refs]
index a2bf985a36a8..24a5c8c5cb8a 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: b599cbdf1c2d88eac7caed00854ee4eecb119a6b
+refs/heads/master: bc56620b493496b8a6962080b644ccc537f4d526
diff --git a/trunk/mm/ksm.c b/trunk/mm/ksm.c
index c059ca1c9356..0320327b8a6c 100644
--- a/trunk/mm/ksm.c
+++ b/trunk/mm/ksm.c
@@ -150,23 +150,25 @@ struct stable_node {
  * struct rmap_item - reverse mapping item for virtual addresses
  * @rmap_list: next rmap_item in mm_slot's singly-linked rmap_list
  * @anon_vma: pointer to anon_vma for this mm,address, when in stable tree
+ * @nid: NUMA node id of unstable tree in which linked (may not match page)
  * @mm: the memory structure this rmap_item is pointing into
  * @address: the virtual address this rmap_item tracks (+ flags in low bits)
  * @oldchecksum: previous checksum of the page at that virtual address
- * @nid: NUMA node id of unstable tree in which linked (may not match page)
  * @node: rb node of this rmap_item in the unstable tree
  * @head: pointer to stable_node heading this list in the stable tree
  * @hlist: link into hlist of rmap_items hanging off that stable_node
  */
 struct rmap_item {
 	struct rmap_item *rmap_list;
-	struct anon_vma *anon_vma;	/* when stable */
+	union {
+		struct anon_vma *anon_vma;	/* when stable */
+#ifdef CONFIG_NUMA
+		int nid;		/* when node of unstable tree */
+#endif
+	};
 	struct mm_struct *mm;
 	unsigned long address;		/* + low bits used for flags below */
 	unsigned int oldchecksum;	/* when unstable */
-#ifdef CONFIG_NUMA
-	int nid;
-#endif
 	union {
 		struct rb_node node;	/* when node of unstable tree */
 		struct {		/* when listed from stable tree */
@@ -1094,6 +1096,9 @@ static int try_to_merge_with_ksm_page(struct rmap_item *rmap_item,
 	if (err)
 		goto out;
 
+	/* Unstable nid is in union with stable anon_vma: remove first */
+	remove_rmap_item_from_tree(rmap_item);
+
 	/* Must get reference to anon_vma while still holding mmap_sem */
 	rmap_item->anon_vma = vma->anon_vma;
 	get_anon_vma(vma->anon_vma);
@@ -1468,14 +1473,11 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item)
 		kpage = try_to_merge_two_pages(rmap_item, page,
 						tree_rmap_item, tree_page);
 		put_page(tree_page);
-		/*
-		 * As soon as we merge this page, we want to remove the
-		 * rmap_item of the page we have merged with from the unstable
-		 * tree, and insert it instead as new node in the stable tree.
-		 */
 		if (kpage) {
-			remove_rmap_item_from_tree(tree_rmap_item);
-
+			/*
+			 * The pages were successfully merged: insert new
+			 * node in the stable tree and add both rmap_items.
+			 */
 			lock_page(kpage);
 			stable_node = stable_tree_insert(kpage);
 			if (stable_node) {