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Date: Fri, 19 Jan 2018 15:12:51 +0100
From: Davide Caratti <dcaratti@...hat.com>
To: "David S. Miller" <davem@...emloft.net>
Cc: netdev@...r.kernel.org, Cong Wang <xiyou.wangcong@...il.com>,
Jiri Pirko <jiri@...nulli.us>
Subject: [PATCH net-next v2 2/2] 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: Davide Caratti <dcaratti@...hat.com>
---
include/net/tc_act/tc_csum.h | 16 ++++++++++--
net/sched/act_csum.c | 58 ++++++++++++++++++++++++++++++++++----------
2 files changed, 59 insertions(+), 15 deletions(-)
diff --git a/include/net/tc_act/tc_csum.h b/include/net/tc_act/tc_csum.h
index 781f3433a0be..9470fd7e4350 100644
--- a/include/net/tc_act/tc_csum.h
+++ b/include/net/tc_act/tc_csum.h
@@ -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 */
diff --git a/net/sched/act_csum.c b/net/sched/act_csum.c
index df22da365cd9..93acbaa2bb25 100644
--- a/net/sched/act_csum.c
+++ b/net/sched/act_csum.c
@@ -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 = rcu_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),
--
2.13.6
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