[PATCH 01/14] net: sched: use rcu for action cookie update

Vlad Buslov
2018-05-14T14:27:45Z

Implement functions to atomically update and free action cookie
using rcu mechanism.

Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
---
include/net/act_api.h | 2 +-
include/net/pkt_cls.h | 1 +
net/sched/act_api.c | 44 ++++++++++++++++++++++++++++++--------------
3 files changed, 32 insertions(+), 15 deletions(-)

diff --git a/include/net/act_api.h b/include/net/act_api.h
index 9e59ebf..f7b59ef 100644
--- a/include/net/act_api.h
+++ b/include/net/act_api.h
@@ -37,7 +37,7 @@ struct tc_action {
spinlock_t tcfa_lock;
struct gnet_stats_basic_cpu __percpu *cpu_bstats;
struct gnet_stats_queue __percpu *cpu_qstats;
- struct tc_cookie *act_cookie;
+ struct tc_cookie __rcu *act_cookie;
struct tcf_chain *goto_chain;
};
#define tcf_index common.tcfa_index
diff --git a/include/net/pkt_cls.h b/include/net/pkt_cls.h
index e828d31..3068cc8 100644
--- a/include/net/pkt_cls.h
+++ b/include/net/pkt_cls.h
@@ -769,6 +769,7 @@ struct tc_mqprio_qopt_offload {
struct tc_cookie {
u8 *data;
u32 len;
+ struct rcu_head rcu;
};

struct tc_qopt_offload_stats {
diff --git a/net/sched/act_api.c b/net/sched/act_api.c
index 72251241..ce829a3 100644
--- a/net/sched/act_api.c
+++ b/net/sched/act_api.c
@@ -55,6 +55,24 @@ static void tcf_action_goto_chain_exec(const struct tc_action *a,
res->goto_tp = rcu_dereference_bh(chain->filter_chain);
}

+static void tcf_free_cookie_rcu(struct rcu_head *p)
+{
+ struct tc_cookie *cookie = container_of(p, struct tc_cookie, rcu);
+
+ kfree(cookie->data);
+ kfree(cookie);
+}
+
+static void tcf_set_action_cookie(struct tc_cookie __rcu **old_cookie,
+ struct tc_cookie *new_cookie)
+{
+ struct tc_cookie *old;
+
+ old = xchg(old_cookie, new_cookie);
+ if (old)
+ call_rcu(&old->rcu, tcf_free_cookie_rcu);
+}
+
/* XXX: For standalone actions, we don't need a RCU grace period either, because
* actions are always connected to filters and filters are already destroyed in
* RCU callbacks, so after a RCU grace period actions are already disconnected
@@ -65,10 +83,7 @@ static void free_tcf(struct tc_action *p)
free_percpu(p->cpu_bstats);
free_percpu(p->cpu_qstats);

- if (p->act_cookie) {
- kfree(p->act_cookie->data);
- kfree(p->act_cookie);
- }
+ tcf_set_action_cookie(&p->act_cookie, NULL);
if (p->goto_chain)
tcf_action_goto_chain_fini(p);

@@ -567,16 +582,22 @@ tcf_action_dump_1(struct sk_buff *skb, struct tc_action *a, int bind, int ref)
int err = -EINVAL;
unsigned char *b = skb_tail_pointer(skb);
struct nlattr *nest;
+ struct tc_cookie *cookie;

if (nla_put_string(skb, TCA_KIND, a->ops->kind))
goto nla_put_failure;
if (tcf_action_copy_stats(skb, a, 0))
goto nla_put_failure;
- if (a->act_cookie) {
- if (nla_put(skb, TCA_ACT_COOKIE, a->act_cookie->len,
- a->act_cookie->data))
+
+ rcu_read_lock();
+ cookie = rcu_dereference(a->act_cookie);
+ if (cookie) {
+ if (nla_put(skb, TCA_ACT_COOKIE, cookie->len, cookie->data)) {
+ rcu_read_unlock();
goto nla_put_failure;
+ }
}
+ rcu_read_unlock();

nest = nla_nest_start(skb, TCA_OPTIONS);
if (nest == NULL)
@@ -719,13 +740,8 @@ struct tc_action *tcf_action_init_1(struct net *net, struct tcf_proto *tp,
if (err < 0)
goto err_mod;

- if (name == NULL && tb[TCA_ACT_COOKIE]) {
- if (a->act_cookie) {
- kfree(a->act_cookie->data);
- kfree(a->act_cookie);
- }
- a->act_cookie = cookie;
- }
+ if (!name && tb[TCA_ACT_COOKIE])
+ tcf_set_action_cookie(&a->act_cookie, cookie);

/* module count goes up only when brand new policy is created
* if it exists and is only bound to in a_o->init() then
--
2.7.5