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_sfb.c b/net/sched/sch_sfb.c
index 9b0f7093d970..1562fb2b3f46 100644
--- a/net/sched/sch_sfb.c
+++ b/net/sched/sch_sfb.c
@@ -55,7 +55,7 @@ struct sfb_bins {
 
 struct sfb_sched_data {
         struct Qdisc    *qdisc;
-        struct tcf_proto *filter_list;
+        struct tcf_proto __rcu *filter_list;
         unsigned long   rehash_interval;
         unsigned long   warmup_time;    /* double buffering warmup time in jiffies */
         u32             max;
@@ -253,13 +253,13 @@ static bool sfb_rate_limit(struct sk_buff *skb, struct sfb_sched_data *q)
         return false;
 }
 
-static bool sfb_classify(struct sk_buff *skb, struct sfb_sched_data *q,
+static bool sfb_classify(struct sk_buff *skb, struct tcf_proto *fl,
                          int *qerr, u32 *salt)
 {
         struct tcf_result res;
         int result;
 
-        result = tc_classify(skb, q->filter_list, &res);
+        result = tc_classify(skb, fl, &res);
         if (result >= 0) {
 #ifdef CONFIG_NET_CLS_ACT
                 switch (result) {
@@ -281,6 +281,7 @@ static int sfb_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 
         struct sfb_sched_data *q = qdisc_priv(sch);
         struct Qdisc *child = q->qdisc;
+        struct tcf_proto *fl;
         int i;
         u32 p_min = ~0;
         u32 minqlen = ~0;
@@ -306,9 +307,10 @@ static int sfb_enqueue(struct sk_buff *skb, struct Qdisc *sch)
                 }
         }
 
-        if (q->filter_list) {
+        fl = rcu_dereference_bh(q->filter_list);
+        if (fl) {
                 /* If using external classifiers, get result and record it. */
-                if (!sfb_classify(skb, q, &ret, &salt))
+                if (!sfb_classify(skb, fl, &ret, &salt))
                         goto other_drop;
                 keys.src = salt;
                 keys.dst = 0;
@@ -660,7 +662,8 @@ static void sfb_walk(struct Qdisc *sch, struct qdisc_walker *walker)
         }
 }
 
-static struct tcf_proto **sfb_find_tcf(struct Qdisc *sch, unsigned long cl)
+static struct tcf_proto __rcu **sfb_find_tcf(struct Qdisc *sch,
+                                             unsigned long cl)
 {
         struct sfb_sched_data *q = qdisc_priv(sch);