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, 9 insertions, 6 deletions

diff --git a/net/sched/sch_choke.c b/net/sched/sch_choke.c
index ed30e436128b..74813e6b6ff6 100644
--- a/net/sched/sch_choke.c
+++ b/net/sched/sch_choke.c
@@ -57,7 +57,7 @@ struct choke_sched_data {
 
 /* Variables */
         struct red_vars  vars;
-        struct tcf_proto *filter_list;
+        struct tcf_proto __rcu *filter_list;
         struct {
                 u32     prob_drop;      /* Early probability drops */
                 u32     prob_mark;      /* Early probability marks */
@@ -193,9 +193,11 @@ static bool choke_classify(struct sk_buff *skb,
 {
         struct choke_sched_data *q = qdisc_priv(sch);
         struct tcf_result res;
+        struct tcf_proto *fl;
         int result;
 
-        result = tc_classify(skb, q->filter_list, &res);
+        fl = rcu_dereference_bh(q->filter_list);
+        result = tc_classify(skb, fl, &res);
         if (result >= 0) {
 #ifdef CONFIG_NET_CLS_ACT
                 switch (result) {
@@ -249,7 +251,7 @@ static bool choke_match_random(const struct choke_sched_data *q,
                 return false;
 
         oskb = choke_peek_random(q, pidx);
-        if (q->filter_list)
+        if (rcu_access_pointer(q->filter_list))
                 return choke_get_classid(nskb) == choke_get_classid(oskb);
 
         return choke_match_flow(oskb, nskb);
@@ -257,11 +259,11 @@ static bool choke_match_random(const struct choke_sched_data *q,
 
 static int choke_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 {
+        int ret = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
         struct choke_sched_data *q = qdisc_priv(sch);
         const struct red_parms *p = &q->parms;
-        int ret = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
 
-        if (q->filter_list) {
+        if (rcu_access_pointer(q->filter_list)) {
                 /* If using external classifiers, get result and record it. */
                 if (!choke_classify(skb, sch, &ret))
                         goto other_drop;        /* Packet was eaten by filter */
@@ -554,7 +556,8 @@ static unsigned long choke_bind(struct Qdisc *sch, unsigned long parent,
         return 0;
 }
 
-static struct tcf_proto **choke_find_tcf(struct Qdisc *sch, unsigned long cl)
+static struct tcf_proto __rcu **choke_find_tcf(struct Qdisc *sch,
+                                               unsigned long cl)
 {
         struct choke_sched_data *q = qdisc_priv(sch);