netdev - Re: [PATCH 2/3] ipvs: avoid rcu_barrier during netns cleanup

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Message-ID: <20131016104306.GA10288@localhost>
Date:	Wed, 16 Oct 2013 12:43:06 +0200
From:	Pablo Neira Ayuso <pablo@...filter.org>
To:	Simon Horman <horms@...ge.net.au>
Cc:	lvs-devel@...r.kernel.org, netdev@...r.kernel.org,
	netfilter-devel@...r.kernel.org,
	Wensong Zhang <wensong@...ux-vs.org>,
	Julian Anastasov <ja@....bg>
Subject: Re: [PATCH 2/3] ipvs: avoid rcu_barrier during netns cleanup

On Tue, Oct 15, 2013 at 11:01:46AM +0900, Simon Horman wrote:
> From: Julian Anastasov <ja@....bg>
> 
> commit 578bc3ef1e473a ("ipvs: reorganize dest trash") added
> rcu_barrier() on cleanup to wait dest users and schedulers
> like LBLC and LBLCR to put their last dest reference.
> Using rcu_barrier with many namespaces is problematic.
> 
> Trying to fix it by freeing dest with kfree_rcu is not
> a solution, RCU callbacks can run in parallel and execution
> order is random.
> 
> Fix it by creating new function ip_vs_dest_put_and_free()
> which is heavier than ip_vs_dest_put(). We will use it just
> for schedulers like LBLC, LBLCR that can delay their dest
> release.
> 
> By default, dests reference is above 0 if they are present in
> service and it is 0 when deleted but still in trash list.
> Change the dest trash code to use ip_vs_dest_put_and_free(),
> so that refcnt -1 can be used for freeing. As result,
> such checks remain in slow path and the rcu_barrier() from
> netns cleanup can be removed.

I can enqueue this fix to nf if you like. No need to resend, I can
manually apply.

Let me know.
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