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, 16 insertions, 14 deletions

diff --git a/net/sched/sch_atm.c b/net/sched/sch_atm.c
index 2732950766a9..c5fcdf1a58a0 100644
--- a/net/sched/sch_atm.c
+++ b/net/sched/sch_atm.c
@@ -108,23 +108,29 @@ static struct Qdisc *atm_tc_leaf(struct Qdisc *sch, unsigned long cl)
 	return flow ? flow->q : NULL;
 }
 
-static unsigned long atm_tc_get(struct Qdisc *sch, u32 classid)
+static unsigned long atm_tc_find(struct Qdisc *sch, u32 classid)
 {
 	struct atm_qdisc_data *p __maybe_unused = qdisc_priv(sch);
 	struct atm_flow_data *flow;
 
-	pr_debug("atm_tc_get(sch %p,[qdisc %p],classid %x)\n", sch, p, classid);
+	pr_debug("%s(sch %p,[qdisc %p],classid %x)\n", __func__, sch, p, classid);
 	flow = lookup_flow(sch, classid);
-	if (flow)
-		flow->ref++;
-	pr_debug("atm_tc_get: flow %p\n", flow);
+	pr_debug("%s: flow %p\n", __func__, flow);
 	return (unsigned long)flow;
 }
 
 static unsigned long atm_tc_bind_filter(struct Qdisc *sch,
 					unsigned long parent, u32 classid)
 {
-	return atm_tc_get(sch, classid);
+	struct atm_qdisc_data *p __maybe_unused = qdisc_priv(sch);
+	struct atm_flow_data *flow;
+
+	pr_debug("%s(sch %p,[qdisc %p],classid %x)\n", __func__, sch, p, classid);
+	flow = lookup_flow(sch, classid);
+	if (flow)
+		flow->ref++;
+	pr_debug("%s: flow %p\n", __func__, flow);
+	return (unsigned long)flow;
 }
 
 /*
@@ -234,7 +240,7 @@ static int atm_tc_change(struct Qdisc *sch, u32 classid, u32 parent,
 		excess = NULL;
 	else {
 		excess = (struct atm_flow_data *)
-			atm_tc_get(sch, nla_get_u32(tb[TCA_ATM_EXCESS]));
+			atm_tc_find(sch, nla_get_u32(tb[TCA_ATM_EXCESS]));
 		if (!excess)
 			return -ENOENT;
 	}
@@ -262,10 +268,9 @@ static int atm_tc_change(struct Qdisc *sch, u32 classid, u32 parent,
 
 		for (i = 1; i < 0x8000; i++) {
 			classid = TC_H_MAKE(sch->handle, 0x8000 | i);
-			cl = atm_tc_get(sch, classid);
+			cl = atm_tc_find(sch, classid);
 			if (!cl)
 				break;
-			atm_tc_put(sch, cl);
 		}
 	}
 	pr_debug("atm_tc_change: new id %x\n", classid);
@@ -305,8 +310,6 @@ static int atm_tc_change(struct Qdisc *sch, u32 classid, u32 parent,
 	*arg = (unsigned long)flow;
 	return 0;
 err_out:
-	if (excess)
-		atm_tc_put(sch, (unsigned long)excess);
 	sockfd_put(sock);
 	return error;
 }
@@ -377,7 +380,7 @@ static int atm_tc_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 	result = TC_ACT_OK;	/* be nice to gcc */
 	flow = NULL;
 	if (TC_H_MAJ(skb->priority) != sch->handle ||
-	    !(flow = (struct atm_flow_data *)atm_tc_get(sch, skb->priority))) {
+	    !(flow = (struct atm_flow_data *)atm_tc_find(sch, skb->priority))) {
 		struct tcf_proto *fl;
 
 		list_for_each_entry(flow, &p->flows, list) {
@@ -655,8 +658,7 @@ static int atm_tc_dump(struct Qdisc *sch, struct sk_buff *skb)
 static const struct Qdisc_class_ops atm_class_ops = {
 	.graft		= atm_tc_graft,
 	.leaf		= atm_tc_leaf,
-	.get		= atm_tc_get,
-	.put		= atm_tc_put,
+	.find		= atm_tc_find,
 	.change		= atm_tc_change,
 	.delete		= atm_tc_delete,
 	.walk		= atm_tc_walk,