kztmem: simplified radix tree data structure support

@@ -0,0 +1,349 @@
+/*
+ * Copyright (C) 2001 Momchil Velikov
+ * Portions Copyright (C) 2001 Christoph Hellwig
+ * Copyright (C) 2005 SGI, Christoph Lameter <[email protected]>
+ * Copyright (C) 2009-2010 simplified/adapted for transcendent memory ("tmem")
+ *      by Dan Magenheimer <[email protected]>, as follows:
+ *
+ * o Linux 2.6.18 source used (prior to read-copy-update addition)
+ * o constants and data structures moved out to sadix-tree.h header
+ * o tagging code removed
+ * o sadix_tree_insert has func parameter for dynamic data struct allocation
+ * o sadix_tree_destroy added (including recursive helper function)
+ * o __init functions must be called explicitly
+ * o sadix_tree_lookup_slot, __lookup and sadix_tree_gang_lookup unused/removed
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2, or (at
+ * your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <linux/module.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include "sadix-tree.h"
+
+static unsigned long height_to_maxindex[SADIX_TREE_MAX_PATH + 1];
+
+/*
+ * Return the maximum key which can be store into a
+ * radix tree with height HEIGHT.
+ */
+static inline unsigned long sadix_tree_maxindex(unsigned int height)
+{
+	return height_to_maxindex[height];
+}
+
+/*
+ * Extend a radix tree so it can store key @index.
+ */
+static int sadix_tree_extend(struct sadix_tree_root *root, unsigned long index,
+				struct sadix_tree_node *(*node_alloc)(void *),
+				void *arg)
+{
+	struct sadix_tree_node *node;
+	unsigned int height;
+
+	/* Figure out what the height should be.  */
+	height = root->height + 1;
+	if (index > sadix_tree_maxindex(height))
+		while (index > sadix_tree_maxindex(height))
+			height++;
+
+	if (root->rnode == NULL) {
+		root->height = height;
+		goto out;
+	}
+
+	do {
+		node = node_alloc(arg);
+		if (!node)
+			return -ENOMEM;
+
+		/* Increase the height.  */
+		node->slots[0] = root->rnode;
+
+		node->count = 1;
+		root->rnode = node;
+		root->height++;
+	} while (height > root->height);
+out:
+	return 0;
+}
+
+/**
+ * sadix_tree_insert    -    insert into a radix tree
+ * @root:  radix tree root
+ * @index:  index key
+ * @item:  item to insert
+ *
+ * Insert an item into the radix tree at position @index.
+ */
+int sadix_tree_insert(struct sadix_tree_root *root, unsigned long index,
+			void *item,
+			struct sadix_tree_node *(*node_alloc)(void *),
+			void *arg)
+{
+	struct sadix_tree_node *node = NULL, *slot;
+	unsigned int height, shift;
+	int offset;
+	int error;
+
+	/* Make sure the tree is high enough.  */
+	if (index > sadix_tree_maxindex(root->height)) {
+		error = sadix_tree_extend(root, index, node_alloc, arg);
+		if (error)
+			return error;
+	}
+
+	slot = root->rnode;
+	height = root->height;
+	shift = (height-1) * SADIX_TREE_MAP_SHIFT;
+
+	offset = 0;   /* uninitialised var warning */
+	while (height > 0) {
+		if (slot == NULL) {
+			/* Have to add a child node.  */
+			slot = node_alloc(arg);
+			if (!slot)
+				return -ENOMEM;
+			if (node) {
+
+				node->slots[offset] = slot;
+				node->count++;
+			} else
+				root->rnode = slot;
+		}
+
+		/* Go a level down */
+		offset = (index >> shift) & SADIX_TREE_MAP_MASK;
+		node = slot;
+		slot = node->slots[offset];
+		shift -= SADIX_TREE_MAP_SHIFT;
+		height--;
+	}
+
+	if (slot != NULL)
+		return -EEXIST;
+
+	if (node) {
+		node->count++;
+		node->slots[offset] = item;
+	} else {
+		root->rnode = item;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(sadix_tree_insert);
+
+static inline void **__lookup_slot(struct sadix_tree_root *root,
+					unsigned long index)
+{
+	unsigned int height, shift;
+	struct sadix_tree_node **slot;
+
+	height = root->height;
+
+	if (index > sadix_tree_maxindex(height))
+		return NULL;
+
+	if (height == 0 && root->rnode)
+		return (void **)&root->rnode;
+
+	shift = (height-1) * SADIX_TREE_MAP_SHIFT;
+	slot = &root->rnode;
+
+	while (height > 0) {
+		if (*slot == NULL)
+			return NULL;
+
+		slot = (struct sadix_tree_node **)
+			((*slot)->slots +
+			 ((index >> shift) & SADIX_TREE_MAP_MASK));
+		shift -= SADIX_TREE_MAP_SHIFT;
+		height--;
+	}
+
+	return (void **)slot;
+}
+
+/**
+ * sadix_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 *sadix_tree_lookup(struct sadix_tree_root *root, unsigned long index)
+{
+	void **slot;
+
+	slot = __lookup_slot(root, index);
+	return slot != NULL ? *slot : NULL;
+}
+EXPORT_SYMBOL(sadix_tree_lookup);
+
+/**
+ * sadix_tree_shrink    -    shrink height of a radix tree to minimal
+ * @root  radix tree root
+ */
+static inline void sadix_tree_shrink(struct sadix_tree_root *root,
+				void (*node_free)(struct sadix_tree_node *))
+{
+	/* try to shrink tree height */
+	while (root->height > 0 &&
+		   root->rnode->count == 1 &&
+		   root->rnode->slots[0]) {
+		struct sadix_tree_node *to_free = root->rnode;
+
+		root->rnode = to_free->slots[0];
+		root->height--;
+		to_free->slots[0] = NULL;
+		to_free->count = 0;
+		node_free(to_free);
+	}
+}
+
+/**
+ * sadix_tree_delete    -    delete an item from a radix tree
+ * @root:  radix tree root
+ * @index:  index key
+ *
+ * Remove the item at @index from the radix tree rooted at @root.
+ *
+ * Returns the address of the deleted item, or NULL if it was not present.
+ */
+void *sadix_tree_delete(struct sadix_tree_root *root, unsigned long index,
+			void(*node_free)(struct sadix_tree_node *))
+{
+	struct sadix_tree_path path[SADIX_TREE_MAX_PATH + 1], *pathp = path;
+	struct sadix_tree_node *slot = NULL;
+	unsigned int height, shift;
+	int offset;
+
+	height = root->height;
+	if (index > sadix_tree_maxindex(height))
+		goto out;
+
+	slot = root->rnode;
+	if (height == 0 && root->rnode) {
+		root->rnode = NULL;
+		goto out;
+	}
+
+	shift = (height - 1) * SADIX_TREE_MAP_SHIFT;
+	pathp->node = NULL;
+
+	do {
+		if (slot == NULL)
+			goto out;
+
+		pathp++;
+		offset = (index >> shift) & SADIX_TREE_MAP_MASK;
+		pathp->offset = offset;
+		pathp->node = slot;
+		slot = slot->slots[offset];
+		shift -= SADIX_TREE_MAP_SHIFT;
+		height--;
+	} while (height > 0);
+
+	if (slot == NULL)
+		goto out;
+
+	/* Now free the nodes we do not need anymore */
+	while (pathp->node) {
+		pathp->node->slots[pathp->offset] = NULL;
+		pathp->node->count--;
+
+		if (pathp->node->count) {
+			if (pathp->node == root->rnode)
+				sadix_tree_shrink(root, node_free);
+			goto out;
+		}
+
+		/* Node with zero slots in use so free it */
+		node_free(pathp->node);
+
+		pathp--;
+	}
+	root->height = 0;
+	root->rnode = NULL;
+
+out:
+	return slot;
+}
+EXPORT_SYMBOL(sadix_tree_delete);
+
+static void
+sadix_tree_node_destroy(struct sadix_tree_node *node, unsigned int height,
+			void (*slot_free)(void *, void *),
+			void (*node_free)(struct sadix_tree_node *),
+			void *slot_extra)
+{
+	int i;
+
+	if (height == 0)
+		return;
+	for (i = 0; i < SADIX_TREE_MAP_SIZE; i++) {
+		if (node->slots[i]) {
+			if (height == 1) {
+				slot_free(node->slots[i], slot_extra);
+				node->slots[i] = NULL;
+				continue;
+			}
+			sadix_tree_node_destroy(node->slots[i], height-1,
+				slot_free, node_free, slot_extra);
+			node_free(node->slots[i]);
+			node->slots[i] = NULL;
+		}
+	}
+}
+
+void sadix_tree_destroy(struct sadix_tree_root *root,
+			void (*slot_free)(void *, void *),
+			void (*node_free)(struct sadix_tree_node *),
+			void *slot_extra)
+{
+	if (root->rnode == NULL)
+		return;
+	if (root->height == 0)
+		slot_free(root->rnode, slot_extra);
+	else {
+		sadix_tree_node_destroy(root->rnode, root->height,
+				slot_free, node_free, slot_extra);
+		node_free(root->rnode);
+		root->height = 0;
+	}
+	root->rnode = NULL;
+	/* caller must delete root if desired */
+}
+EXPORT_SYMBOL(sadix_tree_destroy);
+
+static unsigned long __init __maxindex(unsigned int height)
+{
+	unsigned int tmp = height * SADIX_TREE_MAP_SHIFT;
+	unsigned long index = (~0UL >> (SADIX_TREE_INDEX_BITS - tmp - 1)) >> 1;
+
+	if (tmp >= SADIX_TREE_INDEX_BITS)
+		index = ~0UL;
+	return index;
+}
+
+void __init sadix_tree_init(void)
+{
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(height_to_maxindex); i++)
+		height_to_maxindex[i] = __maxindex(i);
+}

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