From e4b95c41df36befcfd117210900cd790bc2cd048 Mon Sep 17 00:00:00 2001 From: Cong Wang Date: Mon, 6 Nov 2017 13:47:19 -0800 Subject: [PATCH] net_sched: introduce tcf_exts_get_net() and tcf_exts_put_net() Instead of holding netns refcnt in tc actions, we can minimize the holding time by saving it in struct tcf_exts instead. This means we can just hold netns refcnt right before call_rcu() and release it after tcf_exts_destroy() is done. However, because on netns cleanup path we call tcf_proto_destroy() too, obviously we can not hold netns for a zero refcnt, in this case we have to do cleanup synchronously. It is fine for RCU too, the caller cleanup_net() already waits for a grace period. For other cases, refcnt is non-zero and we can safely grab it as normal and release it after we are done. This patch provides two new API for each filter to use: tcf_exts_get_net() and tcf_exts_put_net(). And all filters now can use the following pattern: void __destroy_filter() { tcf_exts_destroy(); tcf_exts_put_net(); // <== release netns refcnt kfree(); } void some_work() { rtnl_lock(); __destroy_filter(); rtnl_unlock(); } void some_rcu_callback() { tcf_queue_work(some_work); } if (tcf_exts_get_net()) // <== hold netns refcnt call_rcu(some_rcu_callback); else __destroy_filter(); Cc: Lucas Bates Cc: Jamal Hadi Salim Cc: Jiri Pirko Signed-off-by: Cong Wang Signed-off-by: David S. Miller --- include/net/pkt_cls.h | 24 ++++++++++++++++++++++++ net/sched/cls_api.c | 1 + 2 files changed, 25 insertions(+) diff --git a/include/net/pkt_cls.h b/include/net/pkt_cls.h index 70ca243..8826747 100644 --- a/include/net/pkt_cls.h +++ b/include/net/pkt_cls.h @@ -94,6 +94,7 @@ struct tcf_exts { __u32 type; /* for backward compat(TCA_OLD_COMPAT) */ int nr_actions; struct tc_action **actions; + struct net *net; #endif /* Map to export classifier specific extension TLV types to the * generic extensions API. Unsupported extensions must be set to 0. @@ -107,6 +108,7 @@ static inline int tcf_exts_init(struct tcf_exts *exts, int action, int police) #ifdef CONFIG_NET_CLS_ACT exts->type = 0; exts->nr_actions = 0; + exts->net = NULL; exts->actions = kcalloc(TCA_ACT_MAX_PRIO, sizeof(struct tc_action *), GFP_KERNEL); if (!exts->actions) @@ -117,6 +119,28 @@ static inline int tcf_exts_init(struct tcf_exts *exts, int action, int police) return 0; } +/* Return false if the netns is being destroyed in cleanup_net(). Callers + * need to do cleanup synchronously in this case, otherwise may race with + * tc_action_net_exit(). Return true for other cases. + */ +static inline bool tcf_exts_get_net(struct tcf_exts *exts) +{ +#ifdef CONFIG_NET_CLS_ACT + exts->net = maybe_get_net(exts->net); + return exts->net != NULL; +#else + return true; +#endif +} + +static inline void tcf_exts_put_net(struct tcf_exts *exts) +{ +#ifdef CONFIG_NET_CLS_ACT + if (exts->net) + put_net(exts->net); +#endif +} + static inline void tcf_exts_to_list(const struct tcf_exts *exts, struct list_head *actions) { diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c index b2d3107..ecbb019 100644 --- a/net/sched/cls_api.c +++ b/net/sched/cls_api.c @@ -927,6 +927,7 @@ int tcf_exts_validate(struct net *net, struct tcf_proto *tp, struct nlattr **tb, exts->actions[i++] = act; exts->nr_actions = i; } + exts->net = net; } #else if ((exts->action && tb[exts->action]) || -- 2.7.4