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, 5 insertions, 27 deletions

diff --git a/net/sched/sch_hfsc.c b/net/sched/sch_hfsc.c
index 15f09cb9f1ff..7c7820d0fdc7 100644
--- a/net/sched/sch_hfsc.c
+++ b/net/sched/sch_hfsc.c
@@ -110,7 +110,6 @@ enum hfsc_class_flags {
 
 struct hfsc_class {
 	struct Qdisc_class_common cl_common;
-	unsigned int	refcnt;		/* usage count */
 
 	struct gnet_stats_basic_packed bstats;
 	struct gnet_stats_queue qstats;
@@ -1045,7 +1044,6 @@ hfsc_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
 		hfsc_change_usc(cl, usc, 0);
 
 	cl->cl_common.classid = classid;
-	cl->refcnt    = 1;
 	cl->sched     = q;
 	cl->cl_parent = parent;
 	cl->qdisc = qdisc_create_dflt(sch->dev_queue,
@@ -1101,13 +1099,9 @@ hfsc_delete_class(struct Qdisc *sch, unsigned long arg)
 	hfsc_purge_queue(sch, cl);
 	qdisc_class_hash_remove(&q->clhash, &cl->cl_common);
 
-	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);
+
+	hfsc_destroy_class(sch, cl);
 	return 0;
 }
 
@@ -1208,23 +1202,9 @@ hfsc_qlen_notify(struct Qdisc *sch, unsigned long arg)
 }
 
 static unsigned long
-hfsc_get_class(struct Qdisc *sch, u32 classid)
-{
-	struct hfsc_class *cl = hfsc_find_class(classid, sch);
-
-	if (cl != NULL)
-		cl->refcnt++;
-
-	return (unsigned long)cl;
-}
-
-static void
-hfsc_put_class(struct Qdisc *sch, unsigned long arg)
+hfsc_search_class(struct Qdisc *sch, u32 classid)
 {
-	struct hfsc_class *cl = (struct hfsc_class *)arg;
-
-	if (--cl->refcnt == 0)
-		hfsc_destroy_class(sch, cl);
+	return (unsigned long)hfsc_find_class(classid, sch);
 }
 
 static unsigned long
@@ -1413,7 +1393,6 @@ hfsc_init_qdisc(struct Qdisc *sch, struct nlattr *opt)
 		goto err_tcf;
 
 	q->root.cl_common.classid = sch->handle;
-	q->root.refcnt  = 1;
 	q->root.sched   = q;
 	q->root.qdisc = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops,
 					  sch->handle);
@@ -1661,8 +1640,7 @@ static const struct Qdisc_class_ops hfsc_class_ops = {
 	.graft		= hfsc_graft_class,
 	.leaf		= hfsc_class_leaf,
 	.qlen_notify	= hfsc_qlen_notify,
-	.get		= hfsc_get_class,
-	.put		= hfsc_put_class,
+	.find		= hfsc_search_class,
 	.bind_tcf	= hfsc_bind_tcf,
 	.unbind_tcf	= hfsc_unbind_tcf,
 	.tcf_block	= hfsc_tcf_block,