radix_tree_replace() replaces an old item with a new item.
This function is invoked from the memory migration code
to replace with a target page with a new page.

Signed-off-by: Hirokazu Takahashi <taka@valinux.co.jp>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
---

 memhotplug-dave/include/linux/radix-tree.h |    1 
 memhotplug-dave/lib/radix-tree.c           |   55 ++++++++++++++++++++++++++++-
 2 files changed, 55 insertions(+), 1 deletion(-)

diff -puN include/linux/radix-tree.h~AA-PM-03-radix-tree-replace include/linux/radix-tree.h
--- memhotplug/include/linux/radix-tree.h~AA-PM-03-radix-tree-replace	2005-07-28 13:50:32.000000000 -0700
+++ memhotplug-dave/include/linux/radix-tree.h	2005-07-28 13:50:32.000000000 -0700
@@ -47,6 +47,7 @@ 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_delete(struct radix_tree_root *, unsigned long);
+void *radix_tree_replace(struct radix_tree_root *, unsigned long, void *);
 unsigned int
 radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
 			unsigned long first_index, unsigned int max_items);
diff -puN lib/radix-tree.c~AA-PM-03-radix-tree-replace lib/radix-tree.c
--- memhotplug/lib/radix-tree.c~AA-PM-03-radix-tree-replace	2005-07-28 13:50:32.000000000 -0700
+++ memhotplug-dave/lib/radix-tree.c	2005-07-28 13:50:32.000000000 -0700
@@ -100,7 +100,13 @@ radix_tree_node_alloc(struct radix_tree_
 static inline void
 radix_tree_node_free(struct radix_tree_node *node)
 {
-	kmem_cache_free(radix_tree_node_cachep, node);
+	struct radix_tree_preload *rtp;
+
+	rtp = &__get_cpu_var(radix_tree_preloads);
+	if (rtp->nr < ARRAY_SIZE(rtp->nodes))
+		rtp->nodes[rtp->nr++] = node;
+	else
+		kmem_cache_free(radix_tree_node_cachep, node);
 }
 
 /*
@@ -733,6 +739,53 @@ out:
 EXPORT_SYMBOL(radix_tree_delete);
 
 /**
+ *	radix_tree_replace    -    replace items in a radix tree
+ *	@root:		radix tree root
+ *	@index:		index key
+ *	@item:		item to insert
+ *
+ *	Replace the item at @index with @item.
+ *	Returns the address of the deleted item, or NULL if it was not present.
+ */
+void *radix_tree_replace(struct radix_tree_root *root,
+					unsigned long index, void *item)
+{
+	struct radix_tree_path path[RADIX_TREE_MAX_PATH], *pathp = path;
+	unsigned int height, shift;
+	void *ret = NULL;
+
+	height = root->height;
+	if (index > radix_tree_maxindex(height))
+		goto out;
+
+	shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
+	pathp->node = NULL;
+	pathp->slot = &root->rnode;
+
+	while (height > 0) {
+		int offset;
+
+		if (*pathp->slot == NULL)
+			goto out;
+
+		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
+		pathp[1].offset = offset;
+		pathp[1].node = *pathp[0].slot;
+		pathp[1].slot = (struct radix_tree_node **)
+				(pathp[1].node->slots + offset);
+		pathp++;
+		shift -= RADIX_TREE_MAP_SHIFT;
+		height--;
+	}
+
+	if ((ret = *pathp[0].slot))
+		*pathp[0].slot = item;
+out:
+	return ret;
+}
+EXPORT_SYMBOL(radix_tree_replace);
+
+/**
  *	radix_tree_tagged - test whether any items in the tree are tagged
  *	@root:		radix tree root
  *	@tag:		tag to test
_