[RFC PATCH v2 09/14] xarray: Implement migration function for objects

[Tobin C. Harding]

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

Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Co-developed-by: Christoph Lameter <cl@xxxxxxxxx>
Signed-off-by: Tobin C. Harding <tobin@xxxxxxxxxx>
---
 lib/radix-tree.c | 13 +++++++++++++
 lib/xarray.c     | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 59 insertions(+)

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 14d51548bea6..9412c2853726 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -1613,6 +1613,17 @@ static int radix_tree_cpu_dead(unsigned int cpu)
 	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;
@@ -1627,4 +1638,6 @@ 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);
 }
diff --git a/lib/xarray.c b/lib/xarray.c
index 6be3acbb861f..6d2657f2e4cb 100644
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -1971,6 +1971,52 @@ 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_RCU_FREE)
+		return;
+
+	new_node = kmem_cache_alloc_node(radix_tree_node_cachep,
+					 GFP_KERNEL, numa_node);
+	if (!new_node)
+		return;
+
+	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();
+}
+
 #ifdef XA_DEBUG
 void xa_dump_node(const struct xa_node *node)
 {
-- 
2.21.0