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_fq_codel.c b/net/sched/sch_fq_codel.c
index cc56c8bb9bed..105cf5557630 100644
--- a/net/sched/sch_fq_codel.c
+++ b/net/sched/sch_fq_codel.c
@@ -52,7 +52,7 @@ struct fq_codel_flow {
 }; /* please try to keep this structure <= 64 bytes */
 
 struct fq_codel_sched_data {
-        struct tcf_proto *filter_list;  /* optional external classifier */
+        struct tcf_proto __rcu *filter_list; /* optional external classifier */
         struct fq_codel_flow *flows;    /* Flows table [flows_cnt] */
         u32             *backlogs;      /* backlog table [flows_cnt] */
         u32             flows_cnt;      /* number of flows */
@@ -85,6 +85,7 @@ static unsigned int fq_codel_classify(struct sk_buff *skb, struct Qdisc *sch,
                                       int *qerr)
 {
         struct fq_codel_sched_data *q = qdisc_priv(sch);
+        struct tcf_proto *filter;
         struct tcf_result res;
         int result;
 
@@ -93,11 +94,12 @@ static unsigned int fq_codel_classify(struct sk_buff *skb, struct Qdisc *sch,
             TC_H_MIN(skb->priority) <= q->flows_cnt)
                 return TC_H_MIN(skb->priority);
 
-        if (!q->filter_list)
+        filter = rcu_dereference(q->filter_list);
+        if (!filter)
                 return fq_codel_hash(q, skb) + 1;
 
         *qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
-        result = tc_classify(skb, q->filter_list, &res);
+        result = tc_classify(skb, filter, &res);
         if (result >= 0) {
 #ifdef CONFIG_NET_CLS_ACT
                 switch (result) {
@@ -496,7 +498,8 @@ static void fq_codel_put(struct Qdisc *q, unsigned long cl)
 {
 }
 
-static struct tcf_proto **fq_codel_find_tcf(struct Qdisc *sch, unsigned long cl)
+static struct tcf_proto __rcu **fq_codel_find_tcf(struct Qdisc *sch,
+                                                  unsigned long cl)
 {
         struct fq_codel_sched_data *q = qdisc_priv(sch);