[PATCH 24/30] radix-tree: Rewrite radix_tree_tag_get

[Matthew Wilcox]

From: Ross Zwisler <ross.zwis...@linux.intel.com>

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

Signed-off-by: Ross Zwisler <ross.zwis...@linux.intel.com>
Signed-off-by: Matthew Wilcox <wi...@linux.intel.com>
---
 lib/radix-tree.c | 44 ++++++++++++++++++--------------------------
 1 file changed, 18 insertions(+), 26 deletions(-)

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index aca7b2814d26..d894654b5ecc 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -838,45 +838,37 @@ EXPORT_SYMBOL(radix_tree_tag_clear);
 int radix_tree_tag_get(struct radix_tree_root *root,
                        unsigned long index, unsigned int tag)
 {
-       unsigned int height, shift;
-       struct radix_tree_node *node;
+       struct radix_tree_node *node, *parent;
+       unsigned long maxindex;
+       unsigned int shift;
 
-       /* check the root's tag bit */
        if (!root_tag_get(root, tag))
                return 0;
 
-       node = rcu_dereference_raw(root->rnode);
+       shift = radix_tree_load_root(root, &node, &maxindex);
+       if (index > maxindex)
+               return 0;
        if (node == NULL)
                return 0;
 
-       if (!radix_tree_is_indirect_ptr(node))
-               return (index == 0);
-       node = indirect_to_ptr(node);
-
-       height = node->path & RADIX_TREE_HEIGHT_MASK;
-       if (index > radix_tree_maxindex(height))
-               return 0;
+       while (radix_tree_is_indirect_ptr(node)) {
+               int offset;
 
-       shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
+               shift -= RADIX_TREE_MAP_SHIFT;
+               offset = (index >> shift) & RADIX_TREE_MAP_MASK;
 
-       for ( ; ; ) {
-               int offset;
+               parent = indirect_to_ptr(node);
+               offset = radix_tree_descend(parent, &node, offset);
 
-               if (node == NULL)
+               if (!node)
                        return 0;
-               node = indirect_to_ptr(node);
-
-               offset = (index >> shift) & RADIX_TREE_MAP_MASK;
-               if (!tag_get(node, tag, offset))
+               if (!tag_get(parent, tag, offset))
                        return 0;
-               if (height == 1)
-                       return 1;
-               node = rcu_dereference_raw(node->slots[offset]);
-               if (!radix_tree_is_indirect_ptr(node))
-                       return 1;
-               shift -= RADIX_TREE_MAP_SHIFT;
-               height--;
+               if (node == RADIX_TREE_RETRY)
+                       break;
        }
+
+       return 1;
 }
 EXPORT_SYMBOL(radix_tree_tag_get);
 
-- 
2.8.0.rc3