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();

Cong Wang committed 9 years ago

Commit e4b95c41 parent c7e460c2 files · +25 −0Browse files

Showing the changes to include (1 of 2 files). Show all

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include/net/pkt_cls.h+24−0

@@ -94,6 +94,7 @@ struct tcf_exts { · 93 unmodified lines
94	94	__u32 type; /* for backward compat(TCA_OLD_COMPAT) */
95	95	int nr_actions;
96	96	struct tc_action **actions;
	97	+ struct net *net;
97	98	#endif
98	99	/* Map to export classifier specific extension TLV types to the
99	100	* 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) · 7 unmodified lines
107	108	#ifdef CONFIG_NET_CLS_ACT
108	109	exts->type = 0;
109	110	exts->nr_actions = 0;
	111	+ exts->net = NULL;
110	112	exts->actions = kcalloc(TCA_ACT_MAX_PRIO, sizeof(struct tc_action *),
111	113	GFP_KERNEL);
112	114	if (!exts->actions)
@@ -117,6 +119,28 @@ static inline int tcf_exts_init(struct tcf_exts *exts, int action, int police) · 4 unmodified lines
117	119	return 0;
118	120	}
119	121
	122	+/* Return false if the netns is being destroyed in cleanup_net(). Callers
	123	+ * need to do cleanup synchronously in this case, otherwise may race with
	124	+ * tc_action_net_exit(). Return true for other cases.
	125	+ */
	126	+static inline bool tcf_exts_get_net(struct tcf_exts *exts)
	127	+{
	128	+#ifdef CONFIG_NET_CLS_ACT
	129	+ exts->net = maybe_get_net(exts->net);
	130	+ return exts->net != NULL;
	131	+#else
	132	+ return true;
	133	+#endif
	134	+}
	135	+
	136	+static inline void tcf_exts_put_net(struct tcf_exts *exts)
	137	+{
	138	+#ifdef CONFIG_NET_CLS_ACT
	139	+ if (exts->net)
	140	+ put_net(exts->net);
	141	+#endif
	142	+}
	143	+
120	144	static inline void tcf_exts_to_list(const struct tcf_exts *exts,
121	145	struct list_head *actions)
122	146	{