linux-kernel - Re: [PATCH] net: openvswitch: use do

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Message-ID: <d2c14a2d-4e7b-d36a-be90-e987b1ea6183@gmail.com>
Date:   Fri, 24 Apr 2020 08:05:34 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Pravin B Shelar <pshelar@....org>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Tonghao Zhang <xiangxia.m.yue@...il.com>
Cc:     netdev@...r.kernel.org, dev@...nvswitch.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: openvswitch: use do_div() for 64-by-32 divisions:



On 4/24/20 5:10 AM, Geert Uytterhoeven wrote:
> On 32-bit architectures (e.g. m68k):
> 
>     ERROR: modpost: "__udivdi3" [net/openvswitch/openvswitch.ko] undefined!
>     ERROR: modpost: "__divdi3" [net/openvswitch/openvswitch.ko] undefined!
> 
> Fixes: e57358873bb5d6ca ("net: openvswitch: use u64 for meter bucket")
> Reported-by: noreply@...erman.id.au
> Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> ---
>  net/openvswitch/meter.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/openvswitch/meter.c b/net/openvswitch/meter.c
> index 915f31123f235c03..3498a5ab092ab2b8 100644
> --- a/net/openvswitch/meter.c
> +++ b/net/openvswitch/meter.c
> @@ -393,7 +393,7 @@ static struct dp_meter *dp_meter_create(struct nlattr **a)
>  		 * Start with a full bucket.
>  		 */
>  		band->bucket = (band->burst_size + band->rate) * 1000ULL;
> -		band_max_delta_t = band->bucket / band->rate;
> +		band_max_delta_t = do_div(band->bucket, band->rate);
>  		if (band_max_delta_t > meter->max_delta_t)
>  			meter->max_delta_t = band_max_delta_t;
>  		band++;
> 

This is fascinating... Have you tested this patch ?

Please double check what do_div() return value is supposed to be !

Thanks.