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[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>
This commit is contained in:
Hans Reiser 2005-11-07 00:59:29 -08:00 committed by Linus Torvalds
parent 7361f4d8ca
commit a43313668f
2 changed files with 45 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/linux/radix-tree.h
View File

@ -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,

63
lib/radix-tree.c
View File

@ -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);