netdev - Re: [PATCH][net-next] ipv6: drop container_of when convert dst to rt6

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Message-ID: <20180930113252.7159eedd@shemminger-XPS-13-9360>
Date:   Sun, 30 Sep 2018 11:32:52 +0200
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Li RongQing <lirongqing@...du.com>
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH][net-next] ipv6: drop container_of when convert dst to
 rt6_info

On Sun, 30 Sep 2018 13:02:52 +0800
Li RongQing <lirongqing@...du.com> wrote:

> we can save container_of computation and return dst directly,
> since dst is always first member of struct rt6_info
> 
> Add a BUILD_BUG_ON() to catch any change that could break this
> assertion.
> 
> Signed-off-by: Li RongQing <lirongqing@...du.com>

I don't understand why you are doing this? It is not going to be
faster (or safer) than container_of. container_of provides the
same functionality and is safe against position of the member
in the structure.