Re: [PATCH v3 01/11] net: sched: use rcu for action cookie update

[Marcelo Ricardo Leitner]

On Mon, May 28, 2018 at 12:17:19AM +0300, Vlad Buslov wrote:
> Implement functions to atomically update and free action cookie
> using rcu mechanism.
> 
> Signed-off-by: Vlad Buslov 
> Signed-off-by: Jiri Pirko 

Reviewed-by: Marcelo Ricardo Leitner 

> ---
>  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 9e59ebfded62..f7b59ef7303d 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_indexcommon.tcfa_index
> diff --git a/include/net/pkt_cls.h b/include/net/pkt_cls.h
> index e828d31be5da..3068cc8aa0f1 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 3f4cf930f809..02670c7489e3 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(>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(>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(>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
> 

[PATCH v3 01/11] net: sched: use rcu for action cookie update

[Vlad Buslov]

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

Signed-off-by: Vlad Buslov 
Signed-off-by: Jiri Pirko 
---
 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 9e59ebfded62..f7b59ef7303d 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 e828d31be5da..3068cc8aa0f1 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 3f4cf930f809..02670c7489e3 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(>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(>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(>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