From 8d6bbaada2e0a65f9012ac4c2506460160e7237a Mon Sep 17 00:00:00 2001
From: Yu Kuai <yukuai3@huawei.com>
Date: Mon, 29 Aug 2022 10:22:38 +0800
Subject: [PATCH] blk-throttle: prevent overflow while calculating wait time
Git-commit: 8d6bbaada2e0a65f9012ac4c2506460160e7237a
Patch-mainline: v6.1-rc1
References: git-fixes
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>
Signed-off-by: Coly Li <colyli@suse.de>
---
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 a5e495b67827..353bbd0886ca 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)
--
2.35.3