radix-tree: rewrite radix_tree_tag_clear

Use the new multi-order support functions to rewrite
radix_tree_tag_clear()

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/radix-tree.c

@@ -768,44 +768,40 @@ EXPORT_SYMBOL(radix_tree_tag_set);
 void *radix_tree_tag_clear(struct radix_tree_root *root,
 			unsigned long index, unsigned int tag)
 {
-	struct radix_tree_node *node = NULL;
-	struct radix_tree_node *slot = NULL;
-	unsigned int height, shift;
+	struct radix_tree_node *node, *parent;
+	unsigned long maxindex;
+	unsigned int shift;
 	int uninitialized_var(offset);
 
-	height = root->height;
-	if (index > radix_tree_maxindex(height))
-		goto out;
-
-	shift = height * RADIX_TREE_MAP_SHIFT;
-	slot = root->rnode;
+	shift = radix_tree_load_root(root, &node, &maxindex);
+	if (index > maxindex)
+		return NULL;
 
-	while (shift) {
-		if (slot == NULL)
-			goto out;
-		if (!radix_tree_is_indirect_ptr(slot))
-			break;
-		slot = indirect_to_ptr(slot);
+	parent = NULL;
 
+	while (radix_tree_is_indirect_ptr(node)) {
 		shift -= RADIX_TREE_MAP_SHIFT;
 		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
-		node = slot;
-		slot = slot->slots[offset];
+
+		parent = indirect_to_ptr(node);
+		offset = radix_tree_descend(parent, &node, offset);
 	}
 
-	if (slot == NULL)
+	if (node == NULL)
 		goto out;
 
-	while (node) {
-		if (!tag_get(node, tag, offset))
+	index >>= shift;
+
+	while (parent) {
+		if (!tag_get(parent, tag, offset))
 			goto out;
-		tag_clear(node, tag, offset);
-		if (any_tag_set(node, tag))
+		tag_clear(parent, tag, offset);
+		if (any_tag_set(parent, tag))
 			goto out;
 
 		index >>= RADIX_TREE_MAP_SHIFT;
 		offset = index & RADIX_TREE_MAP_MASK;
-		node = node->parent;
+		parent = parent->parent;
 	}
 
 	/* clear the root's tag bit */
@@ -813,7 +809,7 @@ void *radix_tree_tag_clear(struct radix_tree_root *root,
 		root_tag_clear(root, tag);
 
 out:
-	return slot;
+	return node;
 }
 EXPORT_SYMBOL(radix_tree_tag_clear);