netdev - Re: [PATCH net-next] Fixes: 0e884c7 ipv4: L3 hash-based multipath: tag

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Date:	Mon, 5 Oct 2015 16:35:59 -0700
From:	Tom Herbert <tom@...bertland.com>
To:	Alexander Duyck <alexander.duyck@...il.com>
Cc:	Peter Nørlund <pch@...bogen.com>,
	Linux Kernel Network Developers <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	James Morris <jmorris@...ei.org>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	Patrick McHardy <kaber@...sh.net>
Subject: Re: [PATCH net-next] Fixes: 0e884c7 ipv4: L3 hash-based multipath: tag

On Mon, Oct 5, 2015 at 3:23 PM, Alexander Duyck
<alexander.duyck@...il.com> wrote:
> On 10/05/2015 03:14 PM, Peter Nørlund wrote:
>>
>> commit 0e884c78ee19e902f300ed147083c28a0c6302f0 ("ipv4: L3 hash-based
>> multipath") broke compilation for i386 and arm due to dependency on
>> 64-bit division.
>>
>> The problem is simply solved by using the proper macro for 64-bit
>> divison.
>>
>> Signed-off-by: Peter Nørlund <pch@...bogen.com>
>> ---
>>   net/ipv4/fib_semantics.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
>> index 0c49d2f..52254e8 100644
>> --- a/net/ipv4/fib_semantics.c
>> +++ b/net/ipv4/fib_semantics.c
>> @@ -569,8 +569,8 @@ static void fib_rebalance(struct fib_info *fi)
>>                         upper_bound = -1;
>>                 } else {
>>                         w += nexthop_nh->nh_weight;
>> -                       upper_bound = DIV_ROUND_CLOSEST(2147483648LL * w,
>> -                                                       total) - 1;
>> +                       upper_bound = DIV_ROUND_CLOSEST_ULL(2147483648ULL
>> * w,
>> +                                                           total) - 1;
>>                 }
>>                 atomic_set(&nexthop_nh->nh_upper_bound, upper_bound);
>
>
> Normally the correct comment would include something like the following just
> before the signed-off-by line.
>     Fixes: 0e884c78ee19 ("ipv4: L3 hash-based multipath")
>
> I'm also kind of curious.  Why use 2147483648LL instead of just casting w as
> a u64 and shifting by 31?  It seems like that would be more readable.
>
+1, manifest constant is not good for readability here.

Tom

> Thanks.
>
> - Alex
>
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