diff --git a/thin-provisioning/device_tree.cc b/thin-provisioning/device_tree.cc
index 140536c..ef5d097 100644
--- a/thin-provisioning/device_tree.cc
+++ b/thin-provisioning/device_tree.cc
@@ -10,9 +10,22 @@ using namespace thin_provisioning;
 namespace {
 	using namespace device_tree_detail;
 
+	struct visitor_adapter {
+		visitor_adapter(device_visitor &dv)
+		: dv_(dv) {
+		}
+
+		void visit(btree_path const &path, device_details const &dd) {
+			dv_.visit(path[0], dd);
+		}
+
+	private:
+		device_visitor &dv_;
+	};
+
 	// No op for now, should add sanity checks in here however.
-	struct leaf_visitor {
-		virtual void visit(btree_path const &path, device_details const &dd) {
+	struct noop_visitor : public device_visitor {
+		virtual void visit(block_address dev_id, device_details const &dd) {
 		}
 	};
 
@@ -62,15 +75,26 @@ namespace thin_provisioning {
 			v.visit(*this);
 		}
 	}
-
-	void check_device_tree(device_tree const &tree, damage_visitor &visitor)
-	{
-		block_counter counter;	// FIXME: get rid of this counter arg
-		leaf_visitor vv;
-		ll_damage_visitor dv(visitor);
-
-		btree_visit_values(tree, counter, vv, dv);
-	}
+}
+
+//----------------------------------------------------------------
+
+void
+thin_provisioning::walk_device_tree(device_tree const &tree,
+				    device_tree_detail::device_visitor &vv,
+				    device_tree_detail::damage_visitor &dv)
+{
+	block_counter counter;
+	visitor_adapter av(vv);
+	ll_damage_visitor ll_dv(dv);
+	btree_visit_values(tree, counter, av, ll_dv);
+}
+
+void
+thin_provisioning::check_device_tree(device_tree const &tree, damage_visitor &visitor)
+{
+	noop_visitor vv;
+	walk_device_tree(tree, vv, visitor);
 }
 
 //----------------------------------------------------------------
diff --git a/thin-provisioning/device_tree.h b/thin-provisioning/device_tree.h
index e270b71..320eb73 100644
--- a/thin-provisioning/device_tree.h
+++ b/thin-provisioning/device_tree.h
@@ -4,6 +4,8 @@
 #include "persistent-data/data-structures/btree.h"
 #include "persistent-data/run.h"
 
+using namespace boost;
+
 //----------------------------------------------------------------
 
 namespace thin_provisioning {
@@ -48,6 +50,8 @@ namespace thin_provisioning {
 
 		class damage_visitor {
 		public:
+			typedef shared_ptr<damage_visitor> ptr;
+
 			virtual ~damage_visitor() {}
 
 			void visit(damage const &d) {
@@ -59,10 +63,18 @@ namespace thin_provisioning {
 
 		// FIXME: need to add some more damage types for bad leaf data
 
+		class device_visitor {
+		public:
+			virtual ~device_visitor() {}
+			virtual void visit(block_address dev_id, device_details const &v) = 0;
+		};
 	};
 
 	typedef persistent_data::btree<1, device_tree_detail::device_details_traits> device_tree;
 
+	void walk_device_tree(device_tree const &tree,
+			      device_tree_detail::device_visitor &dev_v,
+			      device_tree_detail::damage_visitor &dv);
 	void check_device_tree(device_tree const &tree,
 			       device_tree_detail::damage_visitor &visitor);
 }