From: Yu Kuai <yukuai3@xxxxxxxxxx>
carryover_ios/bytes[] can be negative in the case that ios are
dispatched in the slice in advance, and then configuration is updated.
For example:
1) set iops limit to 1000, and slice start is 0, slice end is 100ms;
2) current time is 0, and 100 ios are dispatched, those ios will not be
throttled, hence io_disp is 100;
3) still at current time 0, update iops limit to 100, then carryover_ios
is (0 - 100) = -100;
4) then, dispatch a new io at time 0, the expected result is that this
io will wait for 1s. The calculation in tg_within_iops_limit:
io_disp = 0;
io_allowed = calculate_io_allowed + carryover_ios
= 10 + (-100) = -90;
io won't be throttled if (io_disp + 1 < io_allowed) passed.
Before this patch, in step 4) (io_disp + 1 < io_allowed) is passed,
because -90 for unsigned value is very huge, and such io won't be
throttled.
Fix this problem by checking if 'io/bytes_allowed' is negative first.
Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
---
block/blk-throttle.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 5184f17f5129..7c93144d03da 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -825,7 +825,7 @@ static unsigned long tg_within_iops_limit(struct throtl_grp *tg, struct bio *bio
u32 iops_limit)
{
bool rw = bio_data_dir(bio);
- unsigned int io_allowed;
+ int io_allowed;
unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
if (iops_limit == UINT_MAX) {
@@ -838,9 +838,8 @@ static unsigned long tg_within_iops_limit(struct throtl_grp *tg, struct bio *bio
jiffy_elapsed_rnd = roundup(jiffy_elapsed + 1, tg->td->throtl_slice);
io_allowed = calculate_io_allowed(iops_limit, jiffy_elapsed_rnd) +
tg->carryover_ios[rw];
- if (tg->io_disp[rw] + 1 <= io_allowed) {
+ if (io_allowed > 0 && tg->io_disp[rw] + 1 <= io_allowed)
return 0;
- }
/* Calc approx time to dispatch */
jiffy_wait = jiffy_elapsed_rnd - jiffy_elapsed;
@@ -851,7 +850,8 @@ static unsigned long tg_within_bps_limit(struct throtl_grp *tg, struct bio *bio,
u64 bps_limit)
{
bool rw = bio_data_dir(bio);
- u64 bytes_allowed, extra_bytes;
+ long long bytes_allowed;
+ u64 extra_bytes;
unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
unsigned int bio_size = throtl_bio_data_size(bio);
@@ -869,9 +869,8 @@ static unsigned long tg_within_bps_limit(struct throtl_grp *tg, struct bio *bio,
jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, tg->td->throtl_slice);
bytes_allowed = calculate_bytes_allowed(bps_limit, jiffy_elapsed_rnd) +
tg->carryover_bytes[rw];
- if (tg->bytes_disp[rw] + bio_size <= bytes_allowed) {
+ if (bytes_allowed > 0 && tg->bytes_disp[rw] + bio_size <= bytes_allowed)
return 0;
- }
/* Calc approx time to dispatch */
extra_bytes = tg->bytes_disp[rw] + bio_size - bytes_allowed;
--
2.39.2
