net_sched: remove tc class reference counting

For TC classes, their ->get() and ->put() are always paired, and the
reference counting is completely useless, because:

1) For class modification and dumping paths, we already hold RTNL lock,
   so all of these ->get(),->change(),->put() are atomic.

2) For filter bindiing/unbinding, we use other reference counter than
   this one, and they should have RTNL lock too.

3) For ->qlen_notify(), it is special because it is called on ->enqueue()
   path, but we already hold qdisc tree lock there, and we hold this
   tree lock when graft or delete the class too, so it should not be gone
   or changed until we release the tree lock.

Therefore, this patch removes ->get() and ->put(), but:

1) Adds a new ->find() to find the pointer to a class by classid, no
   refcnt.

2) Move the original class destroy upon the last refcnt into ->delete(),
   right after releasing tree lock. This is fine because the class is
   already removed from hash when holding the lock.

For those who also use ->put() as ->unbind(), just rename them to reflect
this change.

Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 7 deletions

diff --git a/net/sched/sch_mq.c b/net/sched/sch_mq.c
index cadfdd4f1e52..f3a3e507422b 100644
--- a/net/sched/sch_mq.c
+++ b/net/sched/sch_mq.c
@@ -165,7 +165,7 @@ static struct Qdisc *mq_leaf(struct Qdisc *sch, unsigned long cl)
 	return dev_queue->qdisc_sleeping;
 }
 
-static unsigned long mq_get(struct Qdisc *sch, u32 classid)
+static unsigned long mq_find(struct Qdisc *sch, u32 classid)
 {
 	unsigned int ntx = TC_H_MIN(classid);
 
@@ -174,10 +174,6 @@ static unsigned long mq_get(struct Qdisc *sch, u32 classid)
 	return ntx;
 }
 
-static void mq_put(struct Qdisc *sch, unsigned long cl)
-{
-}
-
 static int mq_dump_class(struct Qdisc *sch, unsigned long cl,
 			 struct sk_buff *skb, struct tcmsg *tcm)
 {
@@ -223,8 +219,7 @@ static const struct Qdisc_class_ops mq_class_ops = {
 	.select_queue	= mq_select_queue,
 	.graft		= mq_graft,
 	.leaf		= mq_leaf,
-	.get		= mq_get,
-	.put		= mq_put,
+	.find		= mq_find,
 	.walk		= mq_walk,
 	.dump		= mq_dump_class,
 	.dump_stats	= mq_dump_class_stats,