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, 7 insertions, 4 deletions

diff --git a/net/sched/sch_sfq.c b/net/sched/sch_sfq.c
index 211db9017c35..80c36bd54abc 100644
--- a/net/sched/sch_sfq.c
+++ b/net/sched/sch_sfq.c
@@ -125,7 +125,7 @@ struct sfq_sched_data {
         u8              cur_depth;      /* depth of longest slot */
         u8              flags;
         unsigned short  scaled_quantum; /* SFQ_ALLOT_SIZE(quantum) */
-        struct tcf_proto *filter_list;
+        struct tcf_proto __rcu *filter_list;
         sfq_index       *ht;            /* Hash table ('divisor' slots) */
         struct sfq_slot *slots;         /* Flows table ('maxflows' entries) */
 
@@ -187,6 +187,7 @@ static unsigned int sfq_classify(struct sk_buff *skb, struct Qdisc *sch,
 {
         struct sfq_sched_data *q = qdisc_priv(sch);
         struct tcf_result res;
+        struct tcf_proto *fl;
         int result;
 
         if (TC_H_MAJ(skb->priority) == sch->handle &&
@@ -194,13 +195,14 @@ static unsigned int sfq_classify(struct sk_buff *skb, struct Qdisc *sch,
             TC_H_MIN(skb->priority) <= q->divisor)
                 return TC_H_MIN(skb->priority);
 
-        if (!q->filter_list) {
+        fl = rcu_dereference_bh(q->filter_list);
+        if (!fl) {
                 skb_flow_dissect(skb, &sfq_skb_cb(skb)->keys);
                 return sfq_hash(q, skb) + 1;
         }
 
         *qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
-        result = tc_classify(skb, q->filter_list, &res);
+        result = tc_classify(skb, fl, &res);
         if (result >= 0) {
 #ifdef CONFIG_NET_CLS_ACT
                 switch (result) {
@@ -836,7 +838,8 @@ static void sfq_put(struct Qdisc *q, unsigned long cl)
 {
 }
 
-static struct tcf_proto **sfq_find_tcf(struct Qdisc *sch, unsigned long cl)
+static struct tcf_proto __rcu **sfq_find_tcf(struct Qdisc *sch,
+                                             unsigned long cl)
 {
         struct sfq_sched_data *q = qdisc_priv(sch);