static struct o2nm_cluster *to_o2nm_cluster_from_node(struct o2nm_node *node)
{
	/* through the first node_set .parent
	 * mycluster/nodes/mynode == o2nm_cluster->o2nm_node_group->o2nm_node */
	return to_o2nm_cluster(node->nd_item.ci_parent->ci_parent);
}
A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit.