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

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

[Madalin Bucur]

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@freescale.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;
-- 
1.7.0.1

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

[Eric Dumazet]

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@freescale.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.

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

[Bucur Madalin-Cristian-B32716]

> -----Original Message-----
> From: netdev-owner@vger.kernel.org [mailto:netdev-owner@vger.kernel.org] On
> Behalf Of Eric Dumazet
> Sent: Monday, September 12, 2011 4:58 PM
> 
> 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.
> >
> 
> 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.
> 

Indeed, currently __xfrm_garbage_collect() is called through the garbage_collect
callback but also when an event NETDEV_DOWN is received. Maybe we should have
different functions for the two cases, one calling flow_cache_flush_deferred()
and the other flow_cache_flush().