radix-tree: rewrite __radix_tree_lookup

Use the new multi-order support functions to rewrite __radix_tree_lookup()
Signed-off-by: NMatthew Wilcox <willy@linux.intel.com>
Reviewed-by: NRoss Zwisler <ross.zwisler@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: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

lib/radix-tree.c

@@ -634,44 +634,28 @@ void *__radix_tree_lookup(struct radix_tree_root *root, unsigned long index,
 			  struct radix_tree_node **nodep, void ***slotp)
 {
 	struct radix_tree_node *node, *parent;
-	unsigned int height, shift;
+	unsigned long maxindex;
+	unsigned int shift;
 	void **slot;
 
-	node = rcu_dereference_raw(root->rnode);
-	if (node == NULL)
-		return NULL;
-
-	if (!radix_tree_is_indirect_ptr(node)) {
-		if (index > 0)
-			return NULL;
-
-		if (nodep)
-			*nodep = NULL;
-		if (slotp)
-			*slotp = (void **)&root->rnode;
-		return node;
-	}
-	node = indirect_to_ptr(node);
-
-	height = node->path & RADIX_TREE_HEIGHT_MASK;
-	if (index > radix_tree_maxindex(height))
+ restart:
+	parent = NULL;
+	slot = (void **)&root->rnode;
+	shift = radix_tree_load_root(root, &node, &maxindex);
+	if (index > maxindex)
 		return NULL;
 
-	shift = (height-1) * RADIX_TREE_MAP_SHIFT;
-
-	do {
-		parent = node;
-		slot = node->slots + ((index >> shift) & RADIX_TREE_MAP_MASK);
-		node = rcu_dereference_raw(*slot);
-		if (node == NULL)
-			return NULL;
-		if (!radix_tree_is_indirect_ptr(node))
-			break;
-		node = indirect_to_ptr(node);
+	while (radix_tree_is_indirect_ptr(node)) {
+		unsigned offset;
 
+		if (node == RADIX_TREE_RETRY)
+			goto restart;
+		parent = indirect_to_ptr(node);
 		shift -= RADIX_TREE_MAP_SHIFT;
-		height--;
-	} while (height > 0);
+		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
+		offset = radix_tree_descend(parent, &node, offset);
+		slot = parent->slots + offset;
+	}
 
 	if (nodep)
 		*nodep = parent;