mwl_node
struct mwl_node *mn;
mn = kmem_zalloc(sizeof (struct mwl_node), KM_SLEEP);
struct mwl_node *mn = MWL_NODE(ni);
kmem_free(ni, sizeof (struct mwl_node));
#define MWL_NODE(ni) ((struct mwl_node *)(ni))
#define MWL_NODE_CONST(ni) ((const struct mwl_node *)(ni))