net: rcu-ify tcf_proto

rcu'ify tcf_proto this allows calling tc_classify() without holding
any locks. Updaters are protected by RTNL.

This patch prepares the core net_sched infrastracture for running
the classifier/action chains without holding the qdisc lock however
it does nothing to ensure cls_xxx and act_xxx types also work without
locking. Additional patches are required to address the fall out.

Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 5 deletions

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 58bed7599db7..ca6248345937 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -1781,7 +1781,7 @@ int tc_classify_compat(struct sk_buff *skb, const struct tcf_proto *tp,
         __be16 protocol = skb->protocol;
         int err;
 
-        for (; tp; tp = tp->next) {
+        for (; tp; tp = rcu_dereference_bh(tp->next)) {
                 if (tp->protocol != protocol &&
                     tp->protocol != htons(ETH_P_ALL))
                         continue;
@@ -1833,15 +1833,15 @@ void tcf_destroy(struct tcf_proto *tp)
 {
         tp->ops->destroy(tp);
         module_put(tp->ops->owner);
-        kfree(tp);
+        kfree_rcu(tp, rcu);
 }
 
-void tcf_destroy_chain(struct tcf_proto **fl)
+void tcf_destroy_chain(struct tcf_proto __rcu **fl)
 {
         struct tcf_proto *tp;
 
-        while ((tp = *fl) != NULL) {
-                *fl = tp->next;
+        while ((tp = rtnl_dereference(*fl)) != NULL) {
+                RCU_INIT_POINTER(*fl, tp->next);
                 tcf_destroy(tp);
         }
 }