Commit 8d6bbaad authored by Yu Kuai's avatar Yu Kuai Committed by Jens Axboe
Browse files

blk-throttle: prevent overflow while calculating wait time 



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: default avatarYu Kuai <yukuai3@huawei.com>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20220829022240.3348319-3-yukuai1@huaweicloud.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 320fb0f9

block/blk-throttle.c

+3 −5
Original line number Diff line number Diff line
@@ -806,7 +806,7 @@ static bool tg_with_in_bps_limit(struct throtl_grp *tg, struct bio *bio, 
				 u64 bps_limit, unsigned long *wait)

{

	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 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 = roundup(jiffy_elapsed_rnd, tg->td->throtl_slice);



	tmp = bps_limit * jiffy_elapsed_rnd;

	do_div(tmp, HZ);

	bytes_allowed = tmp;

	bytes_allowed = mul_u64_u64_div_u64(bps_limit, (u64)jiffy_elapsed_rnd,

					    (u64)HZ);



	if (tg->bytes_disp[rw] + bio_size <= bytes_allowed) {

		if (wait)