linux-kernel - Re: [PATCH] blk-throttle: Calculate allowed value only when the throttle is enabled

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Message-ID: <ZR29mvoQMxcZcppw@slm.duckdns.org>
Date:   Wed, 4 Oct 2023 09:31:38 -1000
From:   Tejun Heo <tj@...nel.org>
To:     linan666@...weicloud.com
Cc:     josef@...icpanda.com, axboe@...nel.dk, yukuai3@...wei.com,
        cgroups@...r.kernel.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, linan122@...wei.com,
        yi.zhang@...wei.com, houtao1@...wei.com, yangerkun@...wei.com
Subject: Re: [PATCH] blk-throttle: Calculate allowed value only when the
 throttle is enabled

Hello,

On Thu, Sep 28, 2023 at 09:58:58AM +0800, linan666@...weicloud.com wrote:
> From: Li Nan <linan122@...wei.com>
> 
> When the throttle of bps is not enabled, tg_bps_limit() returns U64_MAX,
> which is be used in calculate_bytes_allowed(), and divide 0 error will
> happen.

calculate_bytes_allowed() is just

  return mul_u64_u64_div_u64(bps_limit, (u64)jiffy_elapsed, (u64)HZ); 

The only division is by HZ. How does divide by 0 happen?

Thanks.

-- 
tejun