[PATCH v8 2/4] blk-throttle: prevent overflow while calculating wait time
From: Yu Kuai <hidden>
Date: 2022-08-23 03:20:53
Also in:
cgroups, lkml
Subsystem:
block layer, control group - block io controller (blkio), the rest · Maintainers:
Jens Axboe, Tejun Heo, Josef Bacik, Linus Torvalds
From: Yu Kuai <redacted> 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 <redacted> Acked-by: Tejun Heo <tj@kernel.org> --- block/blk-throttle.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-)
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index f3c9dcab63e2..773a355d3838 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c@@ -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)
--
2.31.1