blk-throttle: remove last_low_overflow_time

last_low_overflow_time is not used anymore after commit bf20ab53
("blk-throttle: remove CONFIG_BLK_DEV_THROTTLING_LOW").
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20240903135149.271857-2-yukuai1@huaweicloud.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-throttle.c

@@ -1611,17 +1611,13 @@ bool __blk_throtl_bio(struct bio *bio)
 	sq = &tg->service_queue;
 
 	while (true) {
-		if (tg->last_low_overflow_time[rw] == 0)
-			tg->last_low_overflow_time[rw] = jiffies;
 		/* throtl is FIFO - if bios are already queued, should queue */
 		if (sq->nr_queued[rw])
 			break;
 
 		/* if above limits, break to queue */
-		if (!tg_may_dispatch(tg, bio, NULL)) {
-			tg->last_low_overflow_time[rw] = jiffies;
+		if (!tg_may_dispatch(tg, bio, NULL))
 			break;
-		}
 
 		/* within limits, let's charge and dispatch directly */
 		throtl_charge_bio(tg, bio);
@@ -1661,8 +1657,6 @@ bool __blk_throtl_bio(struct bio *bio)
 		   tg->io_disp[rw], tg_iops_limit(tg, rw),
 		   sq->nr_queued[READ], sq->nr_queued[WRITE]);
 
-	tg->last_low_overflow_time[rw] = jiffies;
-
 	td->nr_queued[rw]++;
 	throtl_add_bio_tg(bio, qn, tg);
 	throttled = true;

block/blk-throttle.h

@@ -106,8 +106,6 @@ struct throtl_grp {
 	/* Number of bio's dispatched in current slice */
 	unsigned int io_disp[2];
 
-	unsigned long last_low_overflow_time[2];
-
 	uint64_t last_bytes_disp[2];
 	unsigned int last_io_disp[2];