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blk-throttle: prevent overflow while calculating wait time

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There is a problem found by code review in tg_with_in_bps_limit() that
'bps_limit * jiffy_elapsed_rnd' might overflow. Fix the problem by
calling mul_u64_u64_div_u64() instead.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20220829022240.3348319-3-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Yu Kuai 2022-08-29 10:22:38 +08:00 committed by Jens Axboe
parent 320fb0f91e
commit 8d6bbaada2
1 changed files with 3 additions and 5 deletions
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8
block/blk-throttle.c
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@ -806,7 +806,7 @@ static bool tg_with_in_bps_limit(struct throtl_grp *tg, struct bio *bio,
u64 bps_limit, unsigned long *wait) u64 bps_limit, unsigned long *wait)
{ {
bool rw = bio_data_dir(bio); bool rw = bio_data_dir(bio);
u64 bytes_allowed, extra_bytes, tmp; u64 bytes_allowed, extra_bytes;
unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd; unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
unsigned int bio_size = throtl_bio_data_size(bio); unsigned int bio_size = throtl_bio_data_size(bio);
@ -824,10 +824,8 @@ static bool tg_with_in_bps_limit(struct throtl_grp *tg, struct bio *bio,
jiffy_elapsed_rnd = tg->td->throtl_slice; jiffy_elapsed_rnd = tg->td->throtl_slice;
jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, tg->td->throtl_slice); jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, tg->td->throtl_slice);
bytes_allowed = mul_u64_u64_div_u64(bps_limit, (u64)jiffy_elapsed_rnd,
tmp = bps_limit * jiffy_elapsed_rnd; (u64)HZ);
do_div(tmp, HZ);
bytes_allowed = tmp;
if (tg->bytes_disp[rw] + bio_size <= bytes_allowed) { if (tg->bytes_disp[rw] + bio_size <= bytes_allowed) {
if (wait) if (wait)