netdev - Re: [v1 PATCH 0/7] rhashtable: Introduce inlined interface

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Message-ID: <20150320212844.GC23301@gondor.apana.org.au>
Date:	Sat, 21 Mar 2015 08:28:44 +1100
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	David Miller <davem@...emloft.net>
Cc:	tgraf@...g.ch, eric.dumazet@...il.com, kaber@...sh.net,
	netdev@...r.kernel.org
Subject: Re: [v1 PATCH 0/7] rhashtable: Introduce inlined interface

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.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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