[RFC 7/8] xarray: Implement migration function for objects

[Christoph Lameter <cl@linux.com>]

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Implement functions to migrate objects. This is based on
initial code by Matthew Wilcox and was modified to work with
slab object migration.

Signed-off-by: Christoph Lameter <cl@linux.com>

Index: linux/lib/radix-tree.c
===================================================================
--- linux.orig/lib/radix-tree.c
+++ linux/lib/radix-tree.c
@@ -1754,6 +1754,18 @@ static int radix_tree_cpu_dead(unsigned
 	return 0;
 }
 
+
+extern void xa_object_migrate(void *tree_node, int numa_node);
+
+static void radix_tree_migrate(struct kmem_cache *s, void **objects, int nr,
+		int node, void *private)
+{
+	int i;
+
+	for (i=0; i<nr; i++)
+		xa_object_migrate(objects[i], node);
+}
+
 void __init radix_tree_init(void)
 {
 	int ret;
@@ -1766,4 +1778,7 @@ void __init radix_tree_init(void)
 	ret = cpuhp_setup_state_nocalls(CPUHP_RADIX_DEAD, "lib/radix:dead",
 					NULL, radix_tree_cpu_dead);
 	WARN_ON(ret < 0);
+	kmem_cache_setup_mobility(radix_tree_node_cachep,
+					NULL,
+					radix_tree_migrate);
 }
Index: linux/include/linux/xarray.h
===================================================================
--- linux.orig/include/linux/xarray.h
+++ linux/include/linux/xarray.h
@@ -62,6 +62,8 @@ struct xarray {
 
 void __xa_init(struct xarray *, gfp_t flags);
 
+#define XA_FREE ((struct xarray *)1)
+
 /**
  * xa_init() - Initialise an empty XArray.
  * @xa: XArray.
Index: linux/lib/xarray.c
===================================================================
--- linux.orig/lib/xarray.c
+++ linux/lib/xarray.c
@@ -186,6 +186,7 @@ extern void radix_tree_node_rcu_free(str
 static void xa_node_free(struct xa_node *node)
 {
 	XA_BUG_ON(node, !list_empty(&node->private_list));
+	node->array = XA_FREE;
 	call_rcu(&node->rcu_head, radix_tree_node_rcu_free);
 }
 
@@ -1569,6 +1570,51 @@ void xa_destroy(struct xarray *xa)
 }
 EXPORT_SYMBOL(xa_destroy);
 
+void xa_object_migrate(struct xa_node *node, int numa_node)
+{
+	struct xarray *xa = READ_ONCE(node->array);
+	void __rcu **slot;
+	struct xa_node *new_node;
+	int i;
+
+	/* Freed or not yet in tree then skip */
+	if (!xa || xa == XA_FREE)
+		return;
+
+	new_node = kmem_cache_alloc_node(radix_tree_node_cachep, GFP_KERNEL, numa_node);
+
+	xa_lock_irq(xa);
+
+	/* Check again..... */
+	if (xa != node->array || !list_empty(&node->private_list)) {
+		node = new_node;
+		goto unlock;
+	}
+
+	memcpy(new_node, node, sizeof(struct xa_node));
+
+	/* Move pointers to new node */
+	INIT_LIST_HEAD(&new_node->private_list);
+	for (i = 0; i < XA_CHUNK_SIZE; i++) {
+		void *x = xa_entry_locked(xa, new_node, i);
+
+		if (xa_is_node(x))
+			rcu_assign_pointer(xa_to_node(x)->parent, new_node);
+	}
+	if (!new_node->parent)
+		slot = &xa->xa_head;
+	else
+		slot = &xa_parent_locked(xa, new_node)->slots[new_node->offset];
+	rcu_assign_pointer(*slot, xa_mk_node(new_node));
+
+unlock:
+	xa_unlock_irq(xa);
+	xa_node_free(node);
+	rcu_barrier();
+	return;
+
+}
+
 #ifdef XA_DEBUG
 void xa_dump_node(const struct xa_node *node)
 {

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