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: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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 @@
__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 @@
#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 @@
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 @@
exts->actions[i++] = act;
exts->nr_actions = i;
}
+ exts->net = net;
}
#else
if ((exts->action && tb[exts->action]) ||
