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, 8 insertions, 13 deletions

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 3ef4eb578739..e7f8e4bfd4ec 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -153,7 +153,7 @@ int register_qdisc(struct Qdisc_ops *qops)
 	if (qops->cl_ops) {
 		const struct Qdisc_class_ops *cops = qops->cl_ops;
 
-		if (!(cops->get && cops->put && cops->walk && cops->leaf))
+		if (!(cops->find && cops->walk && cops->leaf))
 			goto out_einval;
 
 		if (cops->tcf_block && !(cops->bind_tcf && cops->unbind_tcf))
@@ -320,12 +320,11 @@ static struct Qdisc *qdisc_leaf(struct Qdisc *p, u32 classid)
 
 	if (cops == NULL)
 		return NULL;
-	cl = cops->get(p, classid);
+	cl = cops->find(p, classid);
 
 	if (cl == 0)
 		return NULL;
 	leaf = cops->leaf(p, cl);
-	cops->put(p, cl);
 	return leaf;
 }
 
@@ -756,9 +755,8 @@ void qdisc_tree_reduce_backlog(struct Qdisc *sch, unsigned int n,
 		}
 		cops = sch->ops->cl_ops;
 		if (notify && cops->qlen_notify) {
-			cl = cops->get(sch, parentid);
+			cl = cops->find(sch, parentid);
 			cops->qlen_notify(sch, cl);
-			cops->put(sch, cl);
 		}
 		sch->q.qlen -= n;
 		sch->qstats.backlog -= len;
@@ -955,11 +953,11 @@ skip:
 
 		err = -EOPNOTSUPP;
 		if (cops && cops->graft) {
-			unsigned long cl = cops->get(parent, classid);
-			if (cl) {
+			unsigned long cl = cops->find(parent, classid);
+
+			if (cl)
 				err = cops->graft(parent, cl, new, &old);
-				cops->put(parent, cl);
-			} else
+			else
 				err = -ENOENT;
 		}
 		if (!err)
@@ -1739,7 +1737,7 @@ static int tc_ctl_tclass(struct sk_buff *skb, struct nlmsghdr *n,
 		clid = TC_H_MAKE(qid, clid);
 
 	if (clid)
-		cl = cops->get(q, clid);
+		cl = cops->find(q, clid);
 
 	if (cl == 0) {
 		err = -ENOENT;
@@ -1773,9 +1771,6 @@ static int tc_ctl_tclass(struct sk_buff *skb, struct nlmsghdr *n,
 		tclass_notify(net, skb, n, q, new_cl, RTM_NEWTCLASS);
 
 out:
-	if (cl)
-		cops->put(q, cl);
-
 	return err;
 }