diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 757b620f0f2d..679e08c0714c 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -639,6 +639,8 @@ static inline void throtl_start_new_slice_with_credit(struct throtl_grp *tg,
 {
 	tg->bytes_disp[rw] = 0;
 	tg->io_disp[rw] = 0;
+	tg->carryover_bytes[rw] = 0;
+	tg->carryover_ios[rw] = 0;
 
 	/*
 	 * Previous slice has expired. We must have trimmed it after last
@@ -656,12 +658,17 @@ static inline void throtl_start_new_slice_with_credit(struct throtl_grp *tg,
 		   tg->slice_end[rw], jiffies);
 }
 
-static inline void throtl_start_new_slice(struct throtl_grp *tg, bool rw)
+static inline void throtl_start_new_slice(struct throtl_grp *tg, bool rw,
+					  bool clear_carryover)
 {
 	tg->bytes_disp[rw] = 0;
 	tg->io_disp[rw] = 0;
 	tg->slice_start[rw] = jiffies;
 	tg->slice_end[rw] = jiffies + tg->td->throtl_slice;
+	if (clear_carryover) {
+		tg->carryover_bytes[rw] = 0;
+		tg->carryover_ios[rw] = 0;
+	}
 
 	throtl_log(&tg->service_queue,
 		   "[%c] new slice start=%lu end=%lu jiffies=%lu",
@@ -783,6 +790,41 @@ static u64 calculate_bytes_allowed(u64 bps_limit, unsigned long jiffy_elapsed)
 	return mul_u64_u64_div_u64(bps_limit, (u64)jiffy_elapsed, (u64)HZ);
 }
 
+static void __tg_update_carryover(struct throtl_grp *tg, bool rw)
+{
+	unsigned long jiffy_elapsed = jiffies - tg->slice_start[rw];
+	u64 bps_limit = tg_bps_limit(tg, rw);
+	u32 iops_limit = tg_iops_limit(tg, rw);
+
+	/*
+	 * If config is updated while bios are still throttled, calculate and
+	 * accumulate how many bytes/ios are waited across changes. And
+	 * carryover_bytes/ios will be used to calculate new wait time under new
+	 * configuration.
+	 */
+	if (bps_limit != U64_MAX)
+		tg->carryover_bytes[rw] +=
+			calculate_bytes_allowed(bps_limit, jiffy_elapsed) -
+			tg->bytes_disp[rw];
+	if (iops_limit != UINT_MAX)
+		tg->carryover_ios[rw] +=
+			calculate_io_allowed(iops_limit, jiffy_elapsed) -
+			tg->io_disp[rw];
+}
+
+static void tg_update_carryover(struct throtl_grp *tg)
+{
+	if (tg->service_queue.nr_queued[READ])
+		__tg_update_carryover(tg, READ);
+	if (tg->service_queue.nr_queued[WRITE])
+		__tg_update_carryover(tg, WRITE);
+
+	/* see comments in struct throtl_grp for meaning of these fields. */
+	throtl_log(&tg->service_queue, "%s: %llu %llu %u %u\n", __func__,
+		   tg->carryover_bytes[READ], tg->carryover_bytes[WRITE],
+		   tg->carryover_ios[READ], tg->carryover_ios[WRITE]);
+}
+
 static bool tg_within_iops_limit(struct throtl_grp *tg, struct bio *bio,
 				 u32 iops_limit, unsigned long *wait)
 {
@@ -800,7 +842,8 @@ static bool tg_within_iops_limit(struct throtl_grp *tg, struct bio *bio,
 
 	/* Round up to the next throttle slice, wait time must be nonzero */
 	jiffy_elapsed_rnd = roundup(jiffy_elapsed + 1, tg->td->throtl_slice);
-	io_allowed = calculate_io_allowed(iops_limit, jiffy_elapsed_rnd);
+	io_allowed = calculate_io_allowed(iops_limit, jiffy_elapsed_rnd) +
+		     tg->carryover_ios[rw];
 	if (tg->io_disp[rw] + 1 <= io_allowed) {
 		if (wait)
 			*wait = 0;
@@ -837,7 +880,8 @@ static bool tg_within_bps_limit(struct throtl_grp *tg, struct bio *bio,
 		jiffy_elapsed_rnd = tg->td->throtl_slice;
 
 	jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, tg->td->throtl_slice);
-	bytes_allowed = calculate_bytes_allowed(bps_limit, jiffy_elapsed_rnd);
+	bytes_allowed = calculate_bytes_allowed(bps_limit, jiffy_elapsed_rnd) +
+			tg->carryover_bytes[rw];
 	if (tg->bytes_disp[rw] + bio_size <= bytes_allowed) {
 		if (wait)
 			*wait = 0;
@@ -898,7 +942,7 @@ static bool tg_may_dispatch(struct throtl_grp *tg, struct bio *bio,
 	 * slice and it should be extended instead.
 	 */
 	if (throtl_slice_used(tg, rw) && !(tg->service_queue.nr_queued[rw]))
-		throtl_start_new_slice(tg, rw);
+		throtl_start_new_slice(tg, rw, true);
 	else {
 		if (time_before(tg->slice_end[rw],
 		    jiffies + tg->td->throtl_slice))
@@ -1332,8 +1376,8 @@ static void tg_conf_updated(struct throtl_grp *tg, bool global)
 	 * that a group's limit are dropped suddenly and we don't want to
 	 * account recently dispatched IO with new low rate.
 	 */
-	throtl_start_new_slice(tg, READ);
-	throtl_start_new_slice(tg, WRITE);
+	throtl_start_new_slice(tg, READ, false);
+	throtl_start_new_slice(tg, WRITE, false);
 
 	if (tg->flags & THROTL_TG_PENDING) {
 		tg_update_disptime(tg);
@@ -1361,6 +1405,7 @@ static ssize_t tg_set_conf(struct kernfs_open_file *of,
 		v = U64_MAX;
 
 	tg = blkg_to_tg(ctx.blkg);
+	tg_update_carryover(tg);
 
 	if (is_u64)
 		*(u64 *)((void *)tg + of_cft(of)->private) = v;
@@ -1547,6 +1592,7 @@ static ssize_t tg_set_limit(struct kernfs_open_file *of,
 		return ret;
 
 	tg = blkg_to_tg(ctx.blkg);
+	tg_update_carryover(tg);
 
 	v[0] = tg->bps_conf[READ][index];
 	v[1] = tg->bps_conf[WRITE][index];
diff --git a/block/blk-throttle.h b/block/blk-throttle.h
index 45c6f3c1dfe0..a25e9e356d17 100644
--- a/block/blk-throttle.h
+++ b/block/blk-throttle.h
@@ -121,6 +121,15 @@ struct throtl_grp {
 	uint64_t last_bytes_disp[2];
 	unsigned int last_io_disp[2];
 
+	/*
+	 * The following two fields are updated when new configuration is
+	 * submitted while some bios are still throttled, they record how many
+	 * bytes/ios are waited already in previous configuration, and they will
+	 * be used to calculate wait time under new configuration.
+	 */
+	uint64_t carryover_bytes[2];
+	unsigned int carryover_ios[2];
+
 	unsigned long last_check_time;
 
 	unsigned long latency_target; /* us */
