From: Oleg Nesterov <oleg@redhat.com>
To: Yu Kuai <yukuai1@huaweicloud.com>
Cc: Li Nan <linan666@huaweicloud.com>,
Khazhy Kumykov <khazhy@chromium.org>,
tj@kernel.org, josef@toxicpanda.com, axboe@kernel.dk,
cgroups@vger.kernel.org, linux-block@vger.kernel.org,
linux-kernel@vger.kernel.org, yi.zhang@huawei.com,
houtao1@huawei.com, yangerkun@huawei.com,
"yukuai (C)" <yukuai3@huawei.com>
Subject: Re: [PATCH] blk-throttle: Calculate allowed value only when the throttle is enabled
Date: Sat, 7 Oct 2023 17:16:08 +0200 [thread overview]
Message-ID: <20231007151607.GA24726@redhat.com> (raw)
In-Reply-To: <0a8f34aa-ced9-e613-3e5f-b5e53a3ef3d9@huaweicloud.com>
On 10/07, Yu Kuai wrote:
>
> >>>probably need to remove the mul_u64_u64_div_u64 and check for
> >>>overflow/potential overflow ourselves?
> >
> >probably yes...
>
> How about this?
>
> diff --git a/block/blk-throttle.c b/block/blk-throttle.c
> index 1101fb6f6cc8..5482c316a103 100644
> --- a/block/blk-throttle.c
> +++ b/block/blk-throttle.c
> @@ -723,6 +723,10 @@ static unsigned int calculate_io_allowed(u32
> iops_limit,
>
> static u64 calculate_bytes_allowed(u64 bps_limit, unsigned long
> jiffy_elapsed)
> {
> + if (jiffy_elapsed > HZ &&
> + bps_limit > mul_u64_u64_div_u64(U64_MAX, (u64)HZ,
> (u64)jiffy_elapsed);
> + return U64_MAX;
> +
I can't suggest anything better...
but I do not know if it is possible that HZ > jiffy_elapsed. If yes, then
mul_u64_u64_div_u64() above is not safe too.
Oleg.
next prev parent reply other threads:[~2023-10-07 15:18 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-28 1:58 [PATCH] blk-throttle: Calculate allowed value only when the throttle is enabled linan666
2023-10-04 19:31 ` Tejun Heo
2023-10-04 20:30 ` Khazhy Kumykov
2023-10-04 20:44 ` Khazhy Kumykov
[not found] ` <4ace01e8-6815-29d0-70ce-4632818ca701@huaweicloud.com>
2023-10-05 16:24 ` Oleg Nesterov
2023-10-07 1:23 ` Yu Kuai
2023-10-07 15:16 ` Oleg Nesterov [this message]
2023-10-08 1:26 ` Yu Kuai
2023-10-08 11:36 ` Oleg Nesterov
2023-10-13 21:51 ` Khazhy Kumykov
2023-10-16 1:46 ` Yu Kuai
2023-10-16 20:06 ` Khazhy Kumykov
2023-10-16 21:48 ` Khazhy Kumykov
2023-10-17 2:38 ` Yu Kuai
2023-10-05 17:04 ` Oleg Nesterov
2023-10-05 17:15 ` Khazhy Kumykov
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