kmem_unback
kmem_unback(kernel_object, (vm_offset_t)chunk->addr,
kmem_unback(kernel_object, addr, size);
void kmem_unback(vm_object_t, vm_offset_t, vm_size_t);
kmem_unback(object, addr, i);
kmem_unback(object, addr, i);
kmem_unback(object, start, addr - start);
kmem_unback(kernel_object, addr, size);