linux-kernel - Re: [PATCH net-next] net: disable fragment reassembly if high

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Date:	Sun, 05 Jun 2016 22:57:40 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	mkubecek@...e.cz
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	kuznet@....inr.ac.ru, jmorris@...ei.org, yoshfuji@...ux-ipv6.org,
	kaber@...sh.net
Subject: Re: [PATCH net-next] net: disable fragment reassembly if
 high_thresh is zero

From: Michal Kubecek <mkubecek@...e.cz>
Date: Fri, 27 May 2016 17:53:52 +0200

> Before commit 6d7b857d541e ("net: use lib/percpu_counter API for
> fragmentation mem accounting"), setting the reassembly high threshold
> to 0 prevented fragment reassembly as first fragment would be always
> evicted before second could be added to the queue. While inefficient,
> some users apparently relied on this method.
> 
> Since the commit mentioned above, a percpu counter is used for
> reassembly memory accounting and high batch size avoids taking slow path
> in most common scenarios. As a result, a whole full sized packet can be
> reassembled without the percpu counter's main counter changing its value
> so that even with high_thresh set to 0, fragmented packets can be still
> reassembled and processed.
> 
> Add explicit check preventing reassembly if high threshold is zero.
> 
> Signed-off-by: Michal Kubecek <mkubecek@...e.cz>

Applied, thanks.