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

Browse source 
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@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Davide Caratti 2018-01-22 18:14:32 +01:00 committed by David S. Miller
parent f6052cf2fc
commit 9c5f69bbd7
2 changed files with 59 additions and 15 deletions
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16
include/net/tc_act/tc_csum.h
View file

@ -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 */

58
net/sched/act_csum.c
View file

@ -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),