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, 11 insertions, 9 deletions

diff --git a/net/sched/sch_atm.c b/net/sched/sch_atm.c
index 8449b337f9e3..c398f9c3dbdd 100644
--- a/net/sched/sch_atm.c
+++ b/net/sched/sch_atm.c
@@ -41,7 +41,7 @@
 
 struct atm_flow_data {
         struct Qdisc            *q;     /* FIFO, TBF, etc. */
-        struct tcf_proto        *filter_list;
+        struct tcf_proto __rcu  *filter_list;
         struct atm_vcc          *vcc;   /* VCC; NULL if VCC is closed */
         void                    (*old_pop)(struct atm_vcc *vcc,
                                            struct sk_buff *skb); /* chaining */
@@ -273,7 +273,7 @@ static int atm_tc_change(struct Qdisc *sch, u32 classid, u32 parent,
                 error = -ENOBUFS;
                 goto err_out;
         }
-        flow->filter_list = NULL;
+        RCU_INIT_POINTER(flow->filter_list, NULL);
         flow->q = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops, classid);
         if (!flow->q)
                 flow->q = &noop_qdisc;
@@ -311,7 +311,7 @@ static int atm_tc_delete(struct Qdisc *sch, unsigned long arg)
         pr_debug("atm_tc_delete(sch %p,[qdisc %p],flow %p)\n", sch, p, flow);
         if (list_empty(&flow->list))
                 return -EINVAL;
-        if (flow->filter_list || flow == &p->link)
+        if (rcu_access_pointer(flow->filter_list) || flow == &p->link)
                 return -EBUSY;
         /*
          * Reference count must be 2: one for "keepalive" (set at class
@@ -345,7 +345,8 @@ static void atm_tc_walk(struct Qdisc *sch, struct qdisc_walker *walker)
         }
 }
 
-static struct tcf_proto **atm_tc_find_tcf(struct Qdisc *sch, unsigned long cl)
+static struct tcf_proto __rcu **atm_tc_find_tcf(struct Qdisc *sch,
+                                                unsigned long cl)
 {
         struct atm_qdisc_data *p = qdisc_priv(sch);
         struct atm_flow_data *flow = (struct atm_flow_data *)cl;
@@ -369,11 +370,12 @@ static int atm_tc_enqueue(struct sk_buff *skb, struct Qdisc *sch)
         flow = NULL;
         if (TC_H_MAJ(skb->priority) != sch->handle ||
             !(flow = (struct atm_flow_data *)atm_tc_get(sch, skb->priority))) {
+                struct tcf_proto *fl;
+
                 list_for_each_entry(flow, &p->flows, list) {
-                        if (flow->filter_list) {
-                                result = tc_classify_compat(skb,
-                                                            flow->filter_list,
-                                                            &res);
+                        fl = rcu_dereference_bh(flow->filter_list);
+                        if (fl) {
+                                result = tc_classify_compat(skb, fl, &res);
                                 if (result < 0)
                                         continue;
                                 flow = (struct atm_flow_data *)res.class;
@@ -544,7 +546,7 @@ static int atm_tc_init(struct Qdisc *sch, struct nlattr *opt)
         if (!p->link.q)
                 p->link.q = &noop_qdisc;
         pr_debug("atm_tc_init: link (%p) qdisc %p\n", &p->link, p->link.q);
-        p->link.filter_list = NULL;
+        RCU_INIT_POINTER(p->link.filter_list, NULL);
         p->link.vcc = NULL;
         p->link.sock = NULL;
         p->link.classid = sch->handle;