netdev - Re: [Drbd-dev] [PATCH net-next v2] block/drbd: use nla_put_u64

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Message-ID: <20160504125253.GP16459@soda.linbit>
Date:	Wed, 4 May 2016 14:52:53 +0200
From:	Lars Ellenberg <lars.ellenberg@...bit.com>
To:	Nicolas Dichtel <nicolas.dichtel@...nd.com>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	philipp.reisner@...bit.com, drbd-dev@...ts.linbit.com,
	linux-kernel@...r.kernel.org
Subject: Re: [Drbd-dev] [PATCH net-next v2] block/drbd: use
 nla_put_u64_64bit()

On Wed, May 04, 2016 at 02:49:00PM +0200, Nicolas Dichtel wrote:
> Le 04/05/2016 11:05, Lars Ellenberg a écrit :
> [snip]
> > We don't have an "alignment problem" there, btw.
> > Last time I checked, we did work fine without this alignment magic,
> > we already take care of that, yes, even on affected architectures.
> The code adds several consecutive u64 attributes. The nl attribute header is 4
> bytes, thus the full attribute length is 12 bytes. If the first u64 is aligned
> on 8 (nla_data()), the next one is not aligned on 8: it starts 12 bytes (8 (u64)
> + 4 (nl attr hdr)) after the previous u64.

Yes.  Which in our case is not a problem.
But I don't object to the padding per se,
if that is how things "should be".

I try to understand why you so much object to using 0 as pad.

    Lars