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Commit e4b95c41 authored by Cong Wang's avatar Cong Wang Committed by David S. Miller
Browse files

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 <lucasb@mojatatu.com>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: default avatarCong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c7e460ce

include/net/pkt_cls.h

+24 −0
Original line number Diff line number Diff line
@@ -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)

{

net/sched/cls_api.c

+1 −0
Original line number Diff line number Diff line
@@ -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]) ||