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authorHans Reiser <reiser@namesys.com>2005-11-07 00:59:29 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2005-11-07 07:53:37 -0800
commita43313668f62a06e14c915b8c8994fc8a1257394 (patch)
treeae02e1ae145b3f277ead948c32b8b6d06a4e23d9 /lib/radix-tree.c
parent7361f4d8ca65d23a18ba009b4484612183332c2f (diff)
downloadlinux-linaro-android-a43313668f62a06e14c915b8c8994fc8a1257394.tar.gz
[PATCH] reiser4: add radix_tree_lookup_slot()
Reiser4 uses radix trees to solve a trouble reiser4_readdir has serving nfs requests. Unfortunately, radix tree api lacks an operation suitable for modifying existing entry. This patch adds radix_tree_lookup_slot which returns pointer to found item within the tree. That location can be then updated. Both Nick and Christoph Lameter have patches which need this as well. Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'lib/radix-tree.c')
-rw-r--r--lib/radix-tree.c51
1 files changed, 38 insertions, 13 deletions
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index d1c057e71b6..88511c3805a 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -281,35 +281,60 @@ int radix_tree_insert(struct radix_tree_root *root,
}
EXPORT_SYMBOL(radix_tree_insert);
-/**
- * radix_tree_lookup - perform lookup operation on a radix tree
- * @root: radix tree root
- * @index: index key
- *
- * Lookup the item at the position @index in the radix tree @root.
- */
-void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index)
+static inline void **__lookup_slot(struct radix_tree_root *root,
+ unsigned long index)
{
unsigned int height, shift;
- struct radix_tree_node *slot;
+ struct radix_tree_node **slot;
height = root->height;
if (index > radix_tree_maxindex(height))
return NULL;
shift = (height-1) * RADIX_TREE_MAP_SHIFT;
- slot = root->rnode;
+ slot = &root->rnode;
while (height > 0) {
- if (slot == NULL)
+ if (*slot == NULL)
return NULL;
- slot = slot->slots[(index >> shift) & RADIX_TREE_MAP_MASK];
+ slot = (struct radix_tree_node **)
+ ((*slot)->slots +
+ ((index >> shift) & RADIX_TREE_MAP_MASK));
shift -= RADIX_TREE_MAP_SHIFT;
height--;
}
- return slot;
+ return (void **)slot;
+}
+
+/**
+ * radix_tree_lookup_slot - lookup a slot in a radix tree
+ * @root: radix tree root
+ * @index: index key
+ *
+ * Lookup the slot corresponding to the position @index in the radix tree
+ * @root. This is useful for update-if-exists operations.
+ */
+void **radix_tree_lookup_slot(struct radix_tree_root *root, unsigned long index)
+{
+ return __lookup_slot(root, index);
+}
+EXPORT_SYMBOL(radix_tree_lookup_slot);
+
+/**
+ * radix_tree_lookup - perform lookup operation on a radix tree
+ * @root: radix tree root
+ * @index: index key
+ *
+ * Lookup the item at the position @index in the radix tree @root.
+ */
+void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index)
+{
+ void **slot;
+
+ slot = __lookup_slot(root, index);
+ return slot != NULL ? *slot : NULL;
}
EXPORT_SYMBOL(radix_tree_lookup);