net: sched: cls_api: add filter counter

Maintain a count of filters per block.

Counter updates are protected by cb_lock, which is
also used to protect the offload counters.

Signed-off-by: Asbjørn Sloth Tønnesen <ast@fiberby.net>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/sch_generic.h

@@ -422,6 +422,7 @@ struct tcf_proto {
 	 */
 	spinlock_t		lock;
 	bool			deleting;
+	bool			counted;
 	refcount_t		refcnt;
 	struct rcu_head		rcu;
 	struct hlist_node	destroy_ht_node;
@@ -471,6 +472,7 @@ struct tcf_block {
 	struct flow_block flow_block;
 	struct list_head owner_list;
 	bool keep_dst;
+	atomic_t filtercnt; /* Number of filters */
 	atomic_t skipswcnt; /* Number of skip_sw filters */
 	atomic_t offloadcnt; /* Number of oddloaded filters */
 	unsigned int nooffloaddevcnt; /* Number of devs unable to do offload */

net/sched/cls_api.c

@@ -410,12 +410,30 @@ static void tcf_proto_get(struct tcf_proto *tp)
 	refcount_inc(&tp->refcnt);
 }
 
+static void tcf_block_filter_cnt_update(struct tcf_block *block, bool *counted, bool add)
+{
+	lockdep_assert_not_held(&block->cb_lock);
+
+	down_write(&block->cb_lock);
+	if (*counted != add) {
+		if (add) {
+			atomic_inc(&block->filtercnt);
+			*counted = true;
+		} else {
+			atomic_dec(&block->filtercnt);
+			*counted = false;
+		}
+	}
+	up_write(&block->cb_lock);
+}
+
 static void tcf_chain_put(struct tcf_chain *chain);
 
 static void tcf_proto_destroy(struct tcf_proto *tp, bool rtnl_held,
 			      bool sig_destroy, struct netlink_ext_ack *extack)
 {
 	tp->ops->destroy(tp, rtnl_held, extack);
+	tcf_block_filter_cnt_update(tp->chain->block, &tp->counted, false);
 	if (sig_destroy)
 		tcf_proto_signal_destroyed(tp->chain, tp);
 	tcf_chain_put(tp->chain);
@@ -2364,6 +2382,7 @@ static int tc_new_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
 	err = tp->ops->change(net, skb, tp, cl, t->tcm_handle, tca, &fh,
 			      flags, extack);
 	if (err == 0) {
+		tcf_block_filter_cnt_update(block, &tp->counted, true);
 		tfilter_notify(net, skb, n, tp, block, q, parent, fh,
 			       RTM_NEWTFILTER, false, rtnl_held, extack);
 		tfilter_put(tp, fh);