[rfc -tip] lib,rb-tree - introduce rb_for_each helper

[Cyrill Gorcunov <gorcunov@gmail.com>]

perftools already use a number of opencoded
for() iterators over rbtree. The patch introduce
rb_for_each helper for this purpose.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
---

The real conversion for this macro usage should be
done later.

Also I think having rb_for_each_entry for being used
with container_of inbetween could be convinient as
well.

Anyway if we don't need such a helper -- just drop
the patch.

 include/linux/rbtree.h |    3 +++
 1 file changed, 3 insertions(+)

Index: linux-2.6.git/include/linux/rbtree.h
=====================================================================
--- linux-2.6.git.orig/include/linux/rbtree.h
+++ linux-2.6.git/include/linux/rbtree.h
@@ -145,6 +145,9 @@ extern struct rb_node *rb_prev(const str
 extern struct rb_node *rb_first(const struct rb_root *);
 extern struct rb_node *rb_last(const struct rb_root *);
 
+#define rb_for_each(nd, root) \
+	for (nd = rb_first((root)); nd; nd = rb_next(nd))
+
 /* Fast replacement of a single node without remove/rebalance/add/rebalance */
 extern void rb_replace_node(struct rb_node *victim, struct rb_node *new, 
 			    struct rb_root *root);