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, 8 insertions, 7 deletions

diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c
index aea942ce6008..6d16b9b81c28 100644
--- a/net/sched/sch_htb.c
+++ b/net/sched/sch_htb.c
@@ -103,7 +103,7 @@ struct htb_class {
         u32                     prio;           /* these two are used only by leaves... */
         int                     quantum;        /* but stored for parent-to-leaf return */
 
-        struct tcf_proto        *filter_list;   /* class attached filters */
+        struct tcf_proto __rcu  *filter_list;   /* class attached filters */
         int                     filter_cnt;
         int                     refcnt;         /* usage count of this class */
 
@@ -153,7 +153,7 @@ struct htb_sched {
         int                     rate2quantum;   /* quant = rate / rate2quantum */
 
         /* filters for qdisc itself */
-        struct tcf_proto        *filter_list;
+        struct tcf_proto __rcu  *filter_list;
 
 #define HTB_WARN_TOOMANYEVENTS  0x1
         unsigned int            warned; /* only one warning */
@@ -223,9 +223,9 @@ static struct htb_class *htb_classify(struct sk_buff *skb, struct Qdisc *sch,
                 if (cl->level == 0)
                         return cl;
                 /* Start with inner filter chain if a non-leaf class is selected */
-                tcf = cl->filter_list;
+                tcf = rcu_dereference_bh(cl->filter_list);
         } else {
-                tcf = q->filter_list;
+                tcf = rcu_dereference_bh(q->filter_list);
         }
 
         *qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
@@ -251,7 +251,7 @@ static struct htb_class *htb_classify(struct sk_buff *skb, struct Qdisc *sch,
                         return cl;      /* we hit leaf; return it */
 
                 /* we have got inner class; apply inner filter chain */
-                tcf = cl->filter_list;
+                tcf = rcu_dereference_bh(cl->filter_list);
         }
         /* classification failed; try to use default class */
         cl = htb_find(TC_H_MAKE(TC_H_MAJ(sch->handle), q->defcls), sch);
@@ -1519,11 +1519,12 @@ failure:
         return err;
 }
 
-static struct tcf_proto **htb_find_tcf(struct Qdisc *sch, unsigned long arg)
+static struct tcf_proto __rcu **htb_find_tcf(struct Qdisc *sch,
+                                             unsigned long arg)
 {
         struct htb_sched *q = qdisc_priv(sch);
         struct htb_class *cl = (struct htb_class *)arg;
-        struct tcf_proto **fl = cl ? &cl->filter_list : &q->filter_list;
+        struct tcf_proto __rcu **fl = cl ? &cl->filter_list : &q->filter_list;
 
         return fl;
 }