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

Marcelo Ricardo Leitner
2018-05-28T21:37:45Z

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 <vladbu@mellanox.com>
> Signed-off-by: Jiri Pirko <jiri@mellanox.com>

Reviewed-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.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 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(&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
>