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Message-ID: <bbc5e21f-9e77-41bb-5763-36bd905b52a0@huaweicloud.com>
Date: Tue, 29 Nov 2022 09:14:58 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: Tejun Heo <tj@...nel.org>, Li Jinlin <lijinlin3@...wei.com>
Cc: josef@...icpanda.com, axboe@...nel.dk, cgroups@...r.kernel.org,
linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
liuzhiqiang26@...wei.com, "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH v2] blk-iocost: fix shift-out-of-bounds in
iocg_hick_delay()
Hi,
在 2022/11/29 3:58, Tejun Heo 写道:
> On Mon, Nov 28, 2022 at 11:04:13AM +0800, Li Jinlin wrote:
>> /* calculate the current delay in effect - 1/2 every second */
>> tdelta = now->now - iocg->delay_at;
>> if (iocg->delay)
>> - delay = iocg->delay >> div64_u64(tdelta, USEC_PER_SEC);
>> + delay = iocg->delay >>
>> + min_t(u64, div64_u64(tdelta, USEC_PER_SEC), 63);
>
> I replied earlier but the right thing to do here is setting delay to 0 if
> the shift is >= 64.
Perhaps following change will make more sense?
@@ -1322,18 +1323,19 @@ static bool iocg_kick_delay(struct ioc_gq *iocg,
struct ioc_now *now)
{
struct ioc *ioc = iocg->ioc;
struct blkcg_gq *blkg = iocg_to_blkg(iocg);
- u64 tdelta, delay, new_delay;
+ u64 delay = 0;
+ u64 new_delay;
s64 vover, vover_pct;
u32 hwa;
lockdep_assert_held(&iocg->waitq.lock);
/* calculate the current delay in effect - 1/2 every second */
- tdelta = now->now - iocg->delay_at;
- if (iocg->delay)
+ if (iocg->delay && now->now > iocg->delay_at) {
+ u64 tdelta = now->now - iocg->delay_at;
+
delay = iocg->delay >> div64_u64(tdelta, USEC_PER_SEC);
- else
- delay = 0;
+ }
>
> Thanks.
>
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