netdev - Re: [PATCH net-next] netfilter: nft_counter: rework atomic dump and reset

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Date:   Sun, 11 Dec 2016 10:02:32 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     pablo@...filter.org
Cc:     netfilter-devel@...r.kernel.org, eric.dumazet@...il.com,
        netdev@...r.kernel.org, arnd@...db.de
Subject: Re: [PATCH net-next] netfilter: nft_counter: rework atomic dump
 and reset

From: Pablo Neira Ayuso <pablo@...filter.org>
Date: Sun, 11 Dec 2016 11:43:59 +0100

> Dump and reset doesn't work unless cmpxchg64() is used both from packet
> and control plane paths. This approach is going to be slow though.
> Instead, use a percpu seqcount to fetch counters consistently, then
> subtract bytes and packets in case a reset was requested.
> 
> The cpu that running over the reset code is guaranteed to own this stats
> exclusively, we have to turn counters into signed 64bit though so stats
> update on reset don't get wrong on underflow.
> 
> This patch is based on original sketch from Eric Dumazet.
> 
> Fixes: 43da04a593d8 ("netfilter: nf_tables: atomic dump and reset for stateful objects")
> Suggested-by: Eric Dumazet <eric.dumazet@...il.com>
> Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
> ---
> v2: adjust stats on reset on the current cpu, turn 64bit counters into signed.
> 
> @David: Please, take this into net-next to help speed up thing, thanks!

Applied.