block: revert 4f1e9630afe6 ("blk-throtl: optimize IOPS throttle for large IO scenarios")

Revert commit 4f1e9630afe6 ("blk-throtl: optimize IOPS throttle for large
IO scenarios") since we have another easier way to address this issue and
get better iops throttling result.

Acked-by: Tejun Heo <[e-mail]>
Signed-off-by: Ming Lei <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jens Axboe <[e-mail]>

block/blk-throttle.c

···
 	tg->bytes_disp[rw] = 0;
 	tg->io_disp[rw] = 0;
 
-	atomic_set(&tg->io_split_cnt[rw], 0);
-
 	/*
 	 * Previous slice has expired. We must have trimmed it after last
 	 * bio dispatch. That means since start of last slice, we never used
···
 	tg->io_disp[rw] = 0;
 	tg->slice_start[rw] = jiffies;
 	tg->slice_end[rw] = jiffies + tg->td->throtl_slice;
-
-	atomic_set(&tg->io_split_cnt[rw], 0);
 
 	throtl_log(&tg->service_queue,
 		   "[%c] new slice start=%lu end=%lu jiffies=%lu",
···
 			throtl_extend_slice(tg, rw,
 				jiffies + tg->td->throtl_slice);
 	}
-
-	if (iops_limit != UINT_MAX)
-		tg->io_disp[rw] += atomic_xchg(&tg->io_split_cnt[rw], 0);
 
 	if (tg_with_in_bps_limit(tg, bio, bps_limit, &bps_wait) &&
 	    tg_with_in_iops_limit(tg, bio, iops_limit, &iops_wait)) {
···
 	}
 
 	if (tg->iops[READ][LIMIT_LOW]) {
-		tg->last_io_disp[READ] += atomic_xchg(&tg->last_io_split_cnt[READ], 0);
 		iops = tg->last_io_disp[READ] * HZ / elapsed_time;
 		if (iops >= tg->iops[READ][LIMIT_LOW])
 			tg->last_low_overflow_time[READ] = now;
 	}
 
 	if (tg->iops[WRITE][LIMIT_LOW]) {
-		tg->last_io_disp[WRITE] += atomic_xchg(&tg->last_io_split_cnt[WRITE], 0);
 		iops = tg->last_io_disp[WRITE] * HZ / elapsed_time;
 		if (iops >= tg->iops[WRITE][LIMIT_LOW])
 			tg->last_low_overflow_time[WRITE] = now;
···
 {
 }
 #endif
-
-void blk_throtl_charge_bio_split(struct bio *bio)
-{
-	struct blkcg_gq *blkg = bio->bi_blkg;
-	struct throtl_grp *parent = blkg_to_tg(blkg);
-	struct throtl_service_queue *parent_sq;
-	bool rw = bio_data_dir(bio);
-
-	do {
-		if (!parent->has_rules[rw])
-			break;
-
-		atomic_inc(&parent->io_split_cnt[rw]);
-		atomic_inc(&parent->last_io_split_cnt[rw]);
-
-		parent_sq = parent->service_queue.parent_sq;
-		parent = sq_to_tg(parent_sq);
-	} while (parent);
-}
 
 bool __blk_throtl_bio(struct bio *bio)
 {

block/blk-throttle.h

···
 	unsigned int bad_bio_cnt; /* bios exceeding latency threshold */
 	unsigned long bio_cnt_reset_time;
 
-	atomic_t io_split_cnt[2];
-	atomic_t last_io_split_cnt[2];
-
 	struct blkg_rwstat stat_bytes;
 	struct blkg_rwstat stat_ios;
 };
···
 static inline int blk_throtl_init(struct request_queue *q) { return 0; }
 static inline void blk_throtl_exit(struct request_queue *q) { }
 static inline void blk_throtl_register_queue(struct request_queue *q) { }
-static inline void blk_throtl_charge_bio_split(struct bio *bio) { }
 static inline bool blk_throtl_bio(struct bio *bio) { return false; }
 #else /* CONFIG_BLK_DEV_THROTTLING */
 int blk_throtl_init(struct request_queue *q);
 void blk_throtl_exit(struct request_queue *q);
 void blk_throtl_register_queue(struct request_queue *q);
-void blk_throtl_charge_bio_split(struct bio *bio);
 bool __blk_throtl_bio(struct bio *bio);
 static inline bool blk_throtl_bio(struct bio *bio)
 {