radix-tree: rewrite radix_tree_tag_get

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

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>

1 files changed, 18 insertions, 26 deletions

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index ee56562e0a2d..b1ca74489bc2 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -831,45 +831,37 @@ 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);