QUEUE_FLAG_STATS
if (test_bit(QUEUE_FLAG_STATS, &q->queue_flags) &&
blk_queue_flag_set(QUEUE_FLAG_STATS, q);
blk_queue_flag_clear(QUEUE_FLAG_STATS, q);
blk_queue_flag_clear(QUEUE_FLAG_STATS, q);
blk_queue_flag_set(QUEUE_FLAG_STATS, q);