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authorNick Piggin <nickpiggin@yahoo.com.au>2006-01-08 01:01:41 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2006-01-08 20:13:41 -0800
commita5f51c966720fa519c6ce69b169107dbc5769cdf (patch)
tree084928ba54750ba3959e376988b503f02ca698b8 /lib/radix-tree.c
parentd5274261ea46f0aae93820fe36628249120d2f75 (diff)
downloadlinux-linaro-stable-a5f51c966720fa519c6ce69b169107dbc5769cdf.tar.gz
[PATCH] radix-tree: reduce tree height upon partial truncation
Shrink the height of a radix tree when it is partially truncated - we only do shrinkage of full truncation at present. Signed-off-by: Nick Piggin <npiggin@suse.de> 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.c46
1 files changed, 36 insertions, 10 deletions
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 336852f23592..c0bd4a914803 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -253,7 +253,7 @@ int radix_tree_insert(struct radix_tree_root *root,
shift = (height-1) * RADIX_TREE_MAP_SHIFT;
offset = 0; /* uninitialised var warning */
- while (height > 0) {
+ do {
if (slot == NULL) {
/* Have to add a child node. */
if (!(slot = radix_tree_node_alloc(root)))
@@ -271,18 +271,16 @@ int radix_tree_insert(struct radix_tree_root *root,
slot = node->slots[offset];
shift -= RADIX_TREE_MAP_SHIFT;
height--;
- }
+ } while (height > 0);
if (slot != NULL)
return -EEXIST;
- if (node) {
- node->count++;
- node->slots[offset] = item;
- BUG_ON(tag_get(node, 0, offset));
- BUG_ON(tag_get(node, 1, offset));
- } else
- root->rnode = item;
+ BUG_ON(!node);
+ node->count++;
+ node->slots[offset] = item;
+ BUG_ON(tag_get(node, 0, offset));
+ BUG_ON(tag_get(node, 1, offset));
return 0;
}
@@ -680,6 +678,29 @@ radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
EXPORT_SYMBOL(radix_tree_gang_lookup_tag);
/**
+ * radix_tree_shrink - shrink height of a radix tree to minimal
+ * @root radix tree root
+ */
+static inline void radix_tree_shrink(struct radix_tree_root *root)
+{
+ /* try to shrink tree height */
+ while (root->height > 1 &&
+ root->rnode->count == 1 &&
+ root->rnode->slots[0]) {
+ struct radix_tree_node *to_free = root->rnode;
+
+ root->rnode = to_free->slots[0];
+ root->height--;
+ /* must only free zeroed nodes into the slab */
+ tag_clear(to_free, 0, 0);
+ tag_clear(to_free, 1, 0);
+ to_free->slots[0] = NULL;
+ to_free->count = 0;
+ radix_tree_node_free(to_free);
+ }
+}
+
+/**
* radix_tree_delete - delete an item from a radix tree
* @root: radix tree root
* @index: index key
@@ -755,8 +776,13 @@ void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
/* Now free the nodes we do not need anymore */
for (pathp = orig_pathp; pathp->node; pathp--) {
pathp->node->slots[pathp->offset] = NULL;
- if (--pathp->node->count)
+ pathp->node->count--;
+
+ if (pathp->node->count) {
+ if (pathp->node == root->rnode)
+ radix_tree_shrink(root);
goto out;
+ }
/* Node with zero slots in use so free it */
radix_tree_node_free(pathp->node);