netdev - Re: [RFC/PATCH] net: add deferred flow cache flush function to be used in xfrm

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Date:	Mon, 12 Sep 2011 15:58:07 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	madalin.bucur@...escale.com
Cc:	netdev@...r.kernel.org, davem@...emloft.net, timo.teras@....fi
Subject: Re: [RFC/PATCH] net: add deferred flow cache flush function to be
 used in xfrm

Le lundi 12 septembre 2011 à 15:17 +0300, Madalin Bucur a écrit :
> The xfrm garbage collector calls flow_cache_flush() that might sleep.
> The xfrm garbage collector can be called from softirq context, such as from
> net_rx_action() through ip_forward(). Added flow_cache_flush_deferred()
> function that uses the kernel-global work queue to leave the actual
> cache flush processing outside the softirq context.
> 
> Signed-off-by: Madalin Bucur <madalin.bucur@...escale.com>
> ---
>  include/net/flow.h     |    1 +
>  net/core/flow.c        |   12 ++++++++++++
>  net/xfrm/xfrm_policy.c |    2 +-
>  3 files changed, 14 insertions(+), 1 deletions(-)
> 
> diff --git a/include/net/flow.h b/include/net/flow.h
> index c6d5fe5..7b4bc88 100644
> --- a/include/net/flow.h
> +++ b/include/net/flow.h
> @@ -188,6 +188,7 @@ extern struct flow_cache_object *flow_cache_lookup(
>  		u8 dir, flow_resolve_t resolver, void *ctx);
>  
>  extern void flow_cache_flush(void);
> +extern void flow_cache_flush_deferred(void);
>  extern atomic_t flow_cache_genid;
>  
>  #endif
> diff --git a/net/core/flow.c b/net/core/flow.c
> index 990703b..4edef63 100644
> --- a/net/core/flow.c
> +++ b/net/core/flow.c
> @@ -352,6 +352,18 @@ void flow_cache_flush(void)
>  	put_online_cpus();
>  }
>  
> +static void flow_cache_flush_wq(struct work_struct *work)
> +{
> +	flow_cache_flush();
> +}
> +
> +static DECLARE_WORK(flow_cache_flush_work, flow_cache_flush_wq);
> +
> +void flow_cache_flush_deferred(void)
> +{
> +	schedule_work(&flow_cache_flush_work);
> +}
> +
>  static int __cpuinit flow_cache_cpu_prepare(struct flow_cache *fc, int cpu)
>  {
>  	struct flow_cache_percpu *fcp = per_cpu_ptr(fc->percpu, cpu);
> diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
> index 5ce74a3..62b1af8 100644
> --- a/net/xfrm/xfrm_policy.c
> +++ b/net/xfrm/xfrm_policy.c
> @@ -2274,7 +2274,7 @@ static void __xfrm_garbage_collect(struct net *net)
>  {
>  	struct dst_entry *head, *next;
>  
> -	flow_cache_flush();
> +	flow_cache_flush_deferred();
>  
>  	spin_lock_bh(&xfrm_policy_sk_bundle_lock);
>  	head = xfrm_policy_sk_bundles;

Problem is sometime we dont want to defer and are in process context.

xfrm_dev_event(  event == NETDEV_DOWN) is probably a place we dont want
to defer the garbage collection.



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