lib: do code optimization for radix_tree_lookup() and radix_tree_lookup_slot()

radix_tree_lookup() and radix_tree_lookup_slot() have much the
same code except for the return value.

Introduce radix_tree_lookup_element() to do the real work.

/*
 * is_slot == 1 : search for the slot.
 * is_slot == 0 : search for the node.
 */
static void * radix_tree_lookup_element(struct radix_tree_root *root,
					unsigned long index, int is_slot);

Signed-off-by: Huang Shijie <shijie8@gmail.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 5301a52..23abbd9 100644 (file)
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -351,20 +351,12 @@ int radix_tree_insert(struct radix_tree_root *root,
 }
 EXPORT_SYMBOL(radix_tree_insert);
 
-/**
- *     radix_tree_lookup_slot    -    lookup a slot in a radix tree
- *     @root:          radix tree root
- *     @index:         index key
- *
- *     Returns:  the slot corresponding to the position @index in the
- *     radix tree @root. This is useful for update-if-exists operations.
- *
- *     This function can be called under rcu_read_lock iff the slot is not
- *     modified by radix_tree_replace_slot, otherwise it must be called
- *     exclusive from other writers. Any dereference of the slot must be done
- *     using radix_tree_deref_slot.
+/*
+ * is_slot == 1 : search for the slot.
+ * is_slot == 0 : search for the node.
  */
-void **radix_tree_lookup_slot(struct radix_tree_root *root, unsigned long index)
+static void *radix_tree_lookup_element(struct radix_tree_root *root,
+                               unsigned long index, int is_slot)
 {
        unsigned int height, shift;
        struct radix_tree_node *node, **slot;
@@ -376,7 +368,7 @@ void **radix_tree_lookup_slot(struct radix_tree_root *root, unsigned long index)
        if (!radix_tree_is_indirect_ptr(node)) {
                if (index > 0)
                        return NULL;
-               return (void **)&root->rnode;
+               return is_slot ? (void *)&root->rnode : node;
        }
        node = radix_tree_indirect_to_ptr(node);
 
@@ -397,7 +389,25 @@ void **radix_tree_lookup_slot(struct radix_tree_root *root, unsigned long index)
                height--;
        } while (height > 0);
 
-       return (void **)slot;
+       return is_slot ? (void *)slot:node;
+}
+
+/**
+ *     radix_tree_lookup_slot    -    lookup a slot in a radix tree
+ *     @root:          radix tree root
+ *     @index:         index key
+ *
+ *     Returns:  the slot corresponding to the position @index in the
+ *     radix tree @root. This is useful for update-if-exists operations.
+ *
+ *     This function can be called under rcu_read_lock iff the slot is not
+ *     modified by radix_tree_replace_slot, otherwise it must be called
+ *     exclusive from other writers. Any dereference of the slot must be done
+ *     using radix_tree_deref_slot.
+ */
+void **radix_tree_lookup_slot(struct radix_tree_root *root, unsigned long index)
+{
+       return (void **)radix_tree_lookup_element(root, index, 1);
 }
 EXPORT_SYMBOL(radix_tree_lookup_slot);
 
@@ -415,38 +425,7 @@ EXPORT_SYMBOL(radix_tree_lookup_slot);
  */
 void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index)
 {
-       unsigned int height, shift;
-       struct radix_tree_node *node, **slot;
-
-       node = rcu_dereference(root->rnode);
-       if (node == NULL)
-               return NULL;
-
-       if (!radix_tree_is_indirect_ptr(node)) {
-               if (index > 0)
-                       return NULL;
-               return node;
-       }
-       node = radix_tree_indirect_to_ptr(node);
-
-       height = node->height;
-       if (index > radix_tree_maxindex(height))
-               return NULL;
-
-       shift = (height-1) * RADIX_TREE_MAP_SHIFT;
-
-       do {
-               slot = (struct radix_tree_node **)
-                       (node->slots + ((index>>shift) & RADIX_TREE_MAP_MASK));
-               node = rcu_dereference(*slot);
-               if (node == NULL)
-                       return NULL;
-
-               shift -= RADIX_TREE_MAP_SHIFT;
-               height--;
-       } while (height > 0);
-
-       return node;
+       return radix_tree_lookup_element(root, index, 0);
 }
 EXPORT_SYMBOL(radix_tree_lookup);