From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: [v1 PATCH 0/7] rhashtable: Introduce inlined interface
Date: Fri, 20 Mar 2015 18:17:15 -0400 (EDT)
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From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Sat, 21 Mar 2015 08:28:44 +1100

> On Fri, Mar 20, 2015 at 04:17:43PM -0400, David Miller wrote:
>>
>> Why do you need that trailer[] think in the new netlink code?
>> You only use it in an offsetof() expression and wouldn't sizeof
>> the structure work just fine for that?  This also makes the
>> memset() superfluous in the initializer function.
> 
> Aha I was wating for someone to ask :) Without the trailer it
> gets padded to 16 bytes on x86-64.  I found this out because
> netlink was mysteriously failing due to the extra padding not
> getting zeroed. Designated initializers do not zero padding bytes,
> so you'd need an explicit memset.  Besides, hashing another
> four bytes with jhash that always contained zero seemed wasteful.

Then "offsetof(struct netlink_compare_arg, portid) + sizeof(u32)"?