netdev - Re: [PATCH net] ipv6: remove rt6i

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Date:	Mon, 29 Sep 2014 16:51:46 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	hannes@...essinduktion.org
Cc:	netdev@...r.kernel.org, eric.dumazet@...il.com,
	hideaki@...hifuji.org, vyasevich@...il.com,
	nicolas.dichtel@...nd.com, kafai@...com
Subject: Re: [PATCH net] ipv6: remove rt6i_genid

From: Hannes Frederic Sowa <hannes@...essinduktion.org>
Date: Sun, 28 Sep 2014 00:46:06 +0200

> Eric Dumazet noticed that all no-nonexthop or no-gateway routes which
> are already marked DST_HOST (e.g. input routes routes) will always be
> invalidated during sk_dst_check. Thus per-socket dst caching absolutely
> had no effect and early demuxing had no effect.
> 
> Thus this patch removes rt6i_genid: fn_sernum already gets modified during
> add operations, so we only must ensure we mutate fn_sernum during ipv6
> address remove operations. This is a fairly cost extensive operations,
> but address removal should not happen that often. Also our mtu update
> functions do the same and we heard no complains so far. xfrm policy
> changes also cause a call into fib6_flush_trees. Also plug a hole in
> rt6_info (no cacheline changes).
> 
> I verified via tracing that this change has effect.
> 
> Signed-off-by: Hannes Frederic Sowa <hannes@...essinduktion.org>

Ok, I'll apply this because it does correctly and simply fix the
problem now, thanks.

I'll also queue it up for -stable.

However, longer-term:

>  static inline void rt_genid_bump_ipv6(struct net *net)
>  {
> +	if (__fib6_flush_trees)
> +		__fib6_flush_trees(net);
>  }

I'd really like to see this go away.

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