radix_tree: clean away saw_unset_tag leftovers

radix_tree_tag_get()'s BUG (when it sees a tag after saw_unset_tag) was
unsafe and removed in 2.6.34, but the pointless saw_unset_tag left behind.

Remove it now, and return 0 as soon as we see unset tag - we already rely
upon the root tag to be correct, returning 0 immediately if it's not set.
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/radix-tree.c

@@ -576,7 +576,6 @@ int radix_tree_tag_get(struct radix_tree_root *root,
 {
 	unsigned int height, shift;
 	struct radix_tree_node *node;
-	int saw_unset_tag = 0;
 
 	/* check the root's tag bit */
 	if (!root_tag_get(root, tag))
@@ -603,15 +602,10 @@ int radix_tree_tag_get(struct radix_tree_root *root,
 			return 0;
 
 		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
-
-		/*
-		 * This is just a debug check.  Later, we can bale as soon as
-		 * we see an unset tag.
-		 */
 		if (!tag_get(node, tag, offset))
-			saw_unset_tag = 1;
+			return 0;
 		if (height == 1)
-			return !!tag_get(node, tag, offset);
+			return 1;
 		node = rcu_dereference_raw(node->slots[offset]);
 		shift -= RADIX_TREE_MAP_SHIFT;
 		height--;