allocsp_undo
struct allocsp_undo *next;
struct allocsp_undo *ib_undo = NULL; /* ib undo */
struct allocsp_undo *undo = NULL;
undo = kmem_alloc(sizeof (struct allocsp_undo),
kmem_free(undo, sizeof (struct allocsp_undo));
kmem_free(undo, sizeof (struct allocsp_undo));