net: sched: don't set q pointer for shared blocks

It is pointless to set block->q for block which are shared among
multiple qdiscs. So remove the assignment in that case. Do a bit of code
reshuffle to make block->index initialized at that point so we can use
tcf_block_shared() helper.

Reported-by: Cong Wang <xiyou.wangcong@gmail.com>
Fixes: 4861738775d7 ("net: sched: introduce shared filter blocks infrastructure")
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/cls_api.c

@@ -376,17 +376,12 @@ struct tcf_net {
 static unsigned int tcf_net_id;
 
 static int tcf_block_insert(struct tcf_block *block, struct net *net,
-			    u32 block_index, struct netlink_ext_ack *extack)
+			    struct netlink_ext_ack *extack)
 {
 	struct tcf_net *tn = net_generic(net, tcf_net_id);
-	int err;
 
-	err = idr_alloc_u32(&tn->idr, block, &block_index, block_index,
-			    GFP_KERNEL);
-	if (err)
-		return err;
-	block->index = block_index;
-	return 0;
+	return idr_alloc_u32(&tn->idr, block, &block->index, block->index,
+			     GFP_KERNEL);
 }
 
 static void tcf_block_remove(struct tcf_block *block, struct net *net)
@@ -397,6 +392,7 @@ static void tcf_block_remove(struct tcf_block *block, struct net *net)
 }
 
 static struct tcf_block *tcf_block_create(struct net *net, struct Qdisc *q,
+					  u32 block_index,
 					  struct netlink_ext_ack *extack)
 {
 	struct tcf_block *block;
@@ -419,10 +415,13 @@ static struct tcf_block *tcf_block_create(struct net *net, struct Qdisc *q,
 		err = -ENOMEM;
 		goto err_chain_create;
 	}
-	block->net = qdisc_net(q);
 	block->refcnt = 1;
 	block->net = net;
-	block->q = q;
+	block->index = block_index;
+
+	/* Don't store q pointer for blocks which are shared */
+	if (!tcf_block_shared(block))
+		block->q = q;
 	return block;
 
 err_chain_create:
@@ -518,13 +517,12 @@ int tcf_block_get_ext(struct tcf_block **p_block, struct Qdisc *q,
 	}
 
 	if (!block) {
-		block = tcf_block_create(net, q, extack);
+		block = tcf_block_create(net, q, ei->block_index, extack);
 		if (IS_ERR(block))
 			return PTR_ERR(block);
 		created = true;
-		if (ei->block_index) {
-			err = tcf_block_insert(block, net,
-					       ei->block_index, extack);
+		if (tcf_block_shared(block)) {
+			err = tcf_block_insert(block, net, extack);
 			if (err)
 				goto err_block_insert;
 		}