From: Davide Caratti Date: Mon, 22 Jan 2018 17:14:32 +0000 (+0100) Subject: net/sched: act_csum: don't use spinlock in the fast path X-Git-Tag: v4.16-rc1~123^2~70^2 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=9c5f69bbd75a7db80578782b037629c5f1e59dce;p=linux.git 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 Signed-off-by: David S. Miller --- 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 #include +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..b7ba9b06b147 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 = 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),