diff --git a/mm/interval_tree.c b/mm/interval_tree.c
new file mode 100644
index 0000000..7dc56566
--- /dev/null
+++ b/mm/interval_tree.c
@@ -0,0 +1,61 @@
+/*
+ * mm/interval_tree.c - interval tree for mapping->i_mmap
+ *
+ * Copyright (C) 2012, Michel Lespinasse <walken@google.com>
+ *
+ * This file is released under the GPL v2.
+ */
+
+#include <linux/mm.h>
+#include <linux/fs.h>
+
+#define ITSTRUCT   struct vm_area_struct
+#define ITRB       shared.linear.rb
+#define ITTYPE     unsigned long
+#define ITSUBTREE  shared.linear.rb_subtree_last
+#define ITSTART(n) ((n)->vm_pgoff)
+#define ITLAST(n)  ((n)->vm_pgoff + \
+		    (((n)->vm_end - (n)->vm_start) >> PAGE_SHIFT) - 1)
+#define ITSTATIC
+#define ITPREFIX   vma_interval_tree
+
+#include <linux/interval_tree_tmpl.h>
+
+/* Insert old immediately after vma in the interval tree */
+void vma_interval_tree_add(struct vm_area_struct *vma,
+			   struct vm_area_struct *old,
+			   struct address_space *mapping)
+{
+	struct rb_node **link;
+	struct vm_area_struct *parent;
+	unsigned long last;
+
+	if (unlikely(vma->vm_flags & VM_NONLINEAR)) {
+		list_add(&vma->shared.nonlinear, &old->shared.nonlinear);
+		return;
+	}
+
+	last = ITLAST(vma);
+
+	if (!old->shared.linear.rb.rb_right) {
+		parent = old;
+		link = &old->shared.linear.rb.rb_right;
+	} else {
+		parent = rb_entry(old->shared.linear.rb.rb_right,
+				  struct vm_area_struct, shared.linear.rb);
+		if (parent->shared.linear.rb_subtree_last < last)
+			parent->shared.linear.rb_subtree_last = last;
+		while (parent->shared.linear.rb.rb_left) {
+			parent = rb_entry(parent->shared.linear.rb.rb_left,
+				struct vm_area_struct, shared.linear.rb);
+			if (parent->shared.linear.rb_subtree_last < last)
+				parent->shared.linear.rb_subtree_last = last;
+		}
+		link = &parent->shared.linear.rb.rb_left;
+	}
+
+	vma->shared.linear.rb_subtree_last = last;
+	rb_link_node(&vma->shared.linear.rb, &parent->shared.linear.rb, link);
+	rb_insert_augmented(&vma->shared.linear.rb, &mapping->i_mmap,
+			    &vma_interval_tree_augment_callbacks);
+}