[PATCH] buglet in radix_tree_tag_set

[Peter Zijlstra <peter@programming.kicks-ass.net>]

From: Peter Zijlstra <a.p.zijlstra@chello.nl>

The comment states: 'Setting a tag on a not-present item is a BUG.'
Hence if 'index' is larger than the maxindex; the item _cannot_
be presen; it should also be a BUG.

Also, this allows the following statement (assume a fresh tree):

  radix_tree_tag_set(root, 16, 1);

to fail silently, but when preceded by:

  radix_tree_insert(root, 32, item);

it would BUG, because the height has been extended by the insert.

In neither case was 16 present.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Nick Piggin <npiggin@suse.de>

 lib/radix-tree.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

Index: linux-2.6/lib/radix-tree.c
===================================================================
--- linux-2.6.orig/lib/radix-tree.c	2006-04-07 10:54:43.000000000 +0200
+++ linux-2.6/lib/radix-tree.c	2006-04-28 17:56:14.000000000 +0200
@@ -365,8 +365,7 @@ void *radix_tree_tag_set(struct radix_tr
 	struct radix_tree_node *slot;
 
 	height = root->height;
-	if (index > radix_tree_maxindex(height))
-		return NULL;
+	BUG_ON(index > radix_tree_maxindex(height))
 
 	shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
 	slot = root->rnode;