MEMCG_LRU_HEAD
if (op == MEMCG_LRU_HEAD)
seg = MEMCG_LRU_HEAD;
if (op == MEMCG_LRU_HEAD || op == MEMCG_LRU_OLD)
if (READ_ONCE(lruvec->lrugen.seg) != MEMCG_LRU_HEAD)
lru_gen_rotate_memcg(lruvec, MEMCG_LRU_HEAD);