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, 7 insertions, 26 deletions

diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c
index dcf3c85e1f4f..f955b59d3c7c 100644
--- a/net/sched/sch_htb.c
+++ b/net/sched/sch_htb.c
@@ -107,7 +107,6 @@ struct htb_class {
 	struct tcf_proto __rcu	*filter_list;	/* class attached filters */
 	struct tcf_block	*block;
 	int			filter_cnt;
-	int			refcnt;		/* usage count of this class */
 
 	int			level;		/* our level (see above) */
 	unsigned int		children;
@@ -193,6 +192,10 @@ static inline struct htb_class *htb_find(u32 handle, struct Qdisc *sch)
 	return container_of(clc, struct htb_class, common);
 }
 
+static unsigned long htb_search(struct Qdisc *sch, u32 handle)
+{
+	return (unsigned long)htb_find(handle, sch);
+}
 /**
  * htb_classify - classify a packet into class
  *
@@ -1189,14 +1192,6 @@ static void htb_qlen_notify(struct Qdisc *sch, unsigned long arg)
 	htb_deactivate(qdisc_priv(sch), cl);
 }
 
-static unsigned long htb_get(struct Qdisc *sch, u32 classid)
-{
-	struct htb_class *cl = htb_find(classid, sch);
-	if (cl)
-		cl->refcnt++;
-	return (unsigned long)cl;
-}
-
 static inline int htb_parent_last_child(struct htb_class *cl)
 {
 	if (!cl->parent)
@@ -1316,22 +1311,10 @@ static int htb_delete(struct Qdisc *sch, unsigned long arg)
 	if (last_child)
 		htb_parent_to_leaf(q, cl, new_q);
 
-	BUG_ON(--cl->refcnt == 0);
-	/*
-	 * This shouldn't happen: we "hold" one cops->get() when called
-	 * from tc_ctl_tclass; the destroy method is done from cops->put().
-	 */
-
 	sch_tree_unlock(sch);
-	return 0;
-}
 
-static void htb_put(struct Qdisc *sch, unsigned long arg)
-{
-	struct htb_class *cl = (struct htb_class *)arg;
-
-	if (--cl->refcnt == 0)
-		htb_destroy_class(sch, cl);
+	htb_destroy_class(sch, cl);
+	return 0;
 }
 
 static int htb_change_class(struct Qdisc *sch, u32 classid,
@@ -1422,7 +1405,6 @@ static int htb_change_class(struct Qdisc *sch, u32 classid,
 			}
 		}
 
-		cl->refcnt = 1;
 		cl->children = 0;
 		INIT_LIST_HEAD(&cl->un.leaf.drop_list);
 		RB_CLEAR_NODE(&cl->pq_node);
@@ -1598,8 +1580,7 @@ static const struct Qdisc_class_ops htb_class_ops = {
 	.graft		=	htb_graft,
 	.leaf		=	htb_leaf,
 	.qlen_notify	=	htb_qlen_notify,
-	.get		=	htb_get,
-	.put		=	htb_put,
+	.find		=	htb_search,
 	.change		=	htb_change_class,
 	.delete		=	htb_delete,
 	.walk		=	htb_walk,