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Commit 9c5f69bb authored by Davide Caratti's avatar Davide Caratti Committed by David S. Miller
Browse files

net/sched: act_csum: don't use spinlock in the fast path 



use RCU instead of spin_{,unlock}_bh() to protect concurrent read/write on
act_csum configuration, to reduce the effects of contention in the data
path when multiple readers are present.

Signed-off-by: default avatarDavide Caratti <dcaratti@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent f6052cf2

include/net/tc_act/tc_csum.h

+14 −2
Original line number Diff line number Diff line
@@ -6,10 +6,16 @@ 
#include <net/act_api.h>

#include <linux/tc_act/tc_csum.h>



struct tcf_csum_params {

	int action;

	u32 update_flags;

	struct rcu_head rcu;

};



struct tcf_csum {

	struct tc_action common;



	u32 update_flags;

	struct tcf_csum_params __rcu *params;

};

#define to_tcf_csum(a) ((struct tcf_csum *)a)
@@ -24,7 +30,13 @@ static inline bool is_tcf_csum(const struct tc_action *a) 


static inline u32 tcf_csum_update_flags(const struct tc_action *a)

{

	return to_tcf_csum(a)->update_flags;

	u32 update_flags;



	rcu_read_lock();

	update_flags = rcu_dereference(to_tcf_csum(a)->params)->update_flags;

	rcu_read_unlock();



	return update_flags;

}



#endif /* __NET_TC_CSUM_H */

net/sched/act_csum.c

+45 −13
Original line number Diff line number Diff line
@@ -49,6 +49,7 @@ static int tcf_csum_init(struct net *net, struct nlattr *nla, 
			 int bind)

{

	struct tc_action_net *tn = net_generic(net, csum_net_id);

	struct tcf_csum_params *params_old, *params_new;

	struct nlattr *tb[TCA_CSUM_MAX + 1];

	struct tc_csum *parm;

	struct tcf_csum *p;
@@ -80,10 +81,21 @@ static int tcf_csum_init(struct net *net, struct nlattr *nla, 
	}



	p = to_tcf_csum(*a);

	spin_lock_bh(&p->tcf_lock);

	p->tcf_action = parm->action;

	p->update_flags = parm->update_flags;

	spin_unlock_bh(&p->tcf_lock);

	ASSERT_RTNL();



	params_new = kzalloc(sizeof(*params_new), GFP_KERNEL);

	if (unlikely(!params_new)) {

		if (ret == ACT_P_CREATED)

			tcf_idr_release(*a, bind);

		return -ENOMEM;

	}

	params_old = rtnl_dereference(p->params);



	params_new->action = parm->action;

	params_new->update_flags = parm->update_flags;

	rcu_assign_pointer(p->params, params_new);

	if (params_old)

		kfree_rcu(params_old, rcu);



	if (ret == ACT_P_CREATED)

		tcf_idr_insert(tn, *a);
@@ -539,19 +551,21 @@ static int tcf_csum(struct sk_buff *skb, const struct tc_action *a, 
		    struct tcf_result *res)

{

	struct tcf_csum *p = to_tcf_csum(a);

	int action;

	struct tcf_csum_params *params;

	u32 update_flags;

	int action;



	rcu_read_lock();

	params = rcu_dereference(p->params);



	tcf_lastuse_update(&p->tcf_tm);

	bstats_cpu_update(this_cpu_ptr(p->common.cpu_bstats), skb);

	spin_lock(&p->tcf_lock);

	action = p->tcf_action;

	update_flags = p->update_flags;

	spin_unlock(&p->tcf_lock);



	action = params->action;

	if (unlikely(action == TC_ACT_SHOT))

		goto drop;

		goto drop_stats;



	update_flags = params->update_flags;

	switch (tc_skb_protocol(skb)) {

	case cpu_to_be16(ETH_P_IP):

		if (!tcf_csum_ipv4(skb, update_flags))
@@ -563,11 +577,16 @@ static int tcf_csum(struct sk_buff *skb, const struct tc_action *a, 
		break;

	}



unlock:

	rcu_read_unlock();

	return action;



drop:

	action = TC_ACT_SHOT;



drop_stats:

	qstats_drop_inc(this_cpu_ptr(p->common.cpu_qstats));

	return TC_ACT_SHOT;

	goto unlock;

}



static int tcf_csum_dump(struct sk_buff *skb, struct tc_action *a, int bind,
@@ -575,15 +594,18 @@ static int tcf_csum_dump(struct sk_buff *skb, struct tc_action *a, int bind, 
{

	unsigned char *b = skb_tail_pointer(skb);

	struct tcf_csum *p = to_tcf_csum(a);

	struct tcf_csum_params *params;

	struct tc_csum opt = {

		.update_flags = p->update_flags,

		.index   = p->tcf_index,

		.action  = p->tcf_action,

		.refcnt  = p->tcf_refcnt - ref,

		.bindcnt = p->tcf_bindcnt - bind,

	};

	struct tcf_t t;



	params = rtnl_dereference(p->params);

	opt.action = params->action;

	opt.update_flags = params->update_flags;



	if (nla_put(skb, TCA_CSUM_PARMS, sizeof(opt), &opt))

		goto nla_put_failure;
@@ -598,6 +620,15 @@ static int tcf_csum_dump(struct sk_buff *skb, struct tc_action *a, int bind, 
	return -1;

}



static void tcf_csum_cleanup(struct tc_action *a)

{

	struct tcf_csum *p = to_tcf_csum(a);

	struct tcf_csum_params *params;



	params = rcu_dereference_protected(p->params, 1);

	kfree_rcu(params, rcu);

}



static int tcf_csum_walker(struct net *net, struct sk_buff *skb,

			   struct netlink_callback *cb, int type,

			   const struct tc_action_ops *ops)
@@ -621,6 +652,7 @@ static struct tc_action_ops act_csum_ops = { 
	.act		= tcf_csum,

	.dump		= tcf_csum_dump,

	.init		= tcf_csum_init,

	.cleanup	= tcf_csum_cleanup,

	.walk		= tcf_csum_walker,

	.lookup		= tcf_csum_search,

	.size		= sizeof(struct tcf_csum),