From a43313668f62a06e14c915b8c8994fc8a1257394 Mon Sep 17 00:00:00 2001 From: Hans Reiser Date: Mon, 7 Nov 2005 00:59:29 -0800 Subject: [PATCH] [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 Signed-off-by: Linus Torvalds --- include/linux/radix-tree.h | 1 + lib/radix-tree.c | 63 ++++++++++++++++++++++++++------------ 2 files changed, 45 insertions(+), 19 deletions(-) diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h index 9f0f9281f42a..36e5d269612f 100644 --- a/include/linux/radix-tree.h +++ b/include/linux/radix-tree.h @@ -46,6 +46,7 @@ do { \ int radix_tree_insert(struct radix_tree_root *, unsigned long, void *); void *radix_tree_lookup(struct radix_tree_root *, unsigned long); +void **radix_tree_lookup_slot(struct radix_tree_root *, unsigned long); void *radix_tree_delete(struct radix_tree_root *, unsigned long); unsigned int radix_tree_gang_lookup(struct radix_tree_root *root, void **results, diff --git a/lib/radix-tree.c b/lib/radix-tree.c index d1c057e71b68..88511c3805ad 100644 --- a/lib/radix-tree.c +++ b/lib/radix-tree.c @@ -281,6 +281,47 @@ int radix_tree_insert(struct radix_tree_root *root, } EXPORT_SYMBOL(radix_tree_insert); +static inline void **__lookup_slot(struct radix_tree_root *root, + unsigned long index) +{ + unsigned int height, shift; + 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; + + while (height > 0) { + if (*slot == NULL) + return NULL; + + slot = (struct radix_tree_node **) + ((*slot)->slots + + ((index >> shift) & RADIX_TREE_MAP_MASK)); + shift -= RADIX_TREE_MAP_SHIFT; + height--; + } + + 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 @@ -290,26 +331,10 @@ EXPORT_SYMBOL(radix_tree_insert); */ void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index) { - unsigned int height, shift; - struct radix_tree_node *slot; + void **slot; - height = root->height; - if (index > radix_tree_maxindex(height)) - return NULL; - - shift = (height-1) * RADIX_TREE_MAP_SHIFT; - slot = root->rnode; - - while (height > 0) { - if (slot == NULL) - return NULL; - - slot = slot->slots[(index >> shift) & RADIX_TREE_MAP_MASK]; - shift -= RADIX_TREE_MAP_SHIFT; - height--; - } - - return slot; + slot = __lookup_slot(root, index); + return slot != NULL ? *slot : NULL; } EXPORT_SYMBOL(radix_tree_lookup);