netfilter: flowtable: Make nf_flow_table_offload_add/del_cb inline

Currently, nf_flow_table_offload_add/del_cb are exported by nf_flow_table
module, therefore modules using them will have hard-dependency
on nf_flow_table and will require loading it all the time.

This can lead to an unnecessary overhead on systems that do not
use this API.

To relax the hard-dependency between the modules, we unexport these
functions and make them static inline.

Fixes: 978703f42549 ("netfilter: flowtable: Add API for registering to flow table events")
Signed-off-by: Alaa Hleihel <[e-mail]>
Reviewed-by: Roi Dayan <[e-mail]>
Reviewed-by: Marcelo Ricardo Leitner <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/net/netfilter/nf_flow_table.h

···
 struct flow_offload *flow_offload_alloc(struct nf_conn *ct);
 void flow_offload_free(struct flow_offload *flow);
 
-int nf_flow_table_offload_add_cb(struct nf_flowtable *flow_table,
-				 flow_setup_cb_t *cb, void *cb_priv);
-void nf_flow_table_offload_del_cb(struct nf_flowtable *flow_table,
-				  flow_setup_cb_t *cb, void *cb_priv);
+static inline int
+nf_flow_table_offload_add_cb(struct nf_flowtable *flow_table,
+			     flow_setup_cb_t *cb, void *cb_priv)
+{
+	struct flow_block *block = &flow_table->flow_block;
+	struct flow_block_cb *block_cb;
+	int err = 0;
+
+	down_write(&flow_table->flow_block_lock);
+	block_cb = flow_block_cb_lookup(block, cb, cb_priv);
+	if (block_cb) {
+		err = -EEXIST;
+		goto unlock;
+	}
+
+	block_cb = flow_block_cb_alloc(cb, cb_priv, cb_priv, NULL);
+	if (IS_ERR(block_cb)) {
+		err = PTR_ERR(block_cb);
+		goto unlock;
+	}
+
+	list_add_tail(&block_cb->list, &block->cb_list);
+
+unlock:
+	up_write(&flow_table->flow_block_lock);
+	return err;
+}
+
+static inline void
+nf_flow_table_offload_del_cb(struct nf_flowtable *flow_table,
+			     flow_setup_cb_t *cb, void *cb_priv)
+{
+	struct flow_block *block = &flow_table->flow_block;
+	struct flow_block_cb *block_cb;
+
+	down_write(&flow_table->flow_block_lock);
+	block_cb = flow_block_cb_lookup(block, cb, cb_priv);
+	if (block_cb) {
+		list_del(&block_cb->list);
+		flow_block_cb_free(block_cb);
+	} else {
+		WARN_ON(true);
+	}
+	up_write(&flow_table->flow_block_lock);
+}
 
 int flow_offload_route_init(struct flow_offload *flow,
 			    const struct nf_flow_route *route);

net/netfilter/nf_flow_table_core.c

···
 	queue_delayed_work(system_power_efficient_wq, &flow_table->gc_work, HZ);
 }
 
-int nf_flow_table_offload_add_cb(struct nf_flowtable *flow_table,
-				 flow_setup_cb_t *cb, void *cb_priv)
-{
-	struct flow_block *block = &flow_table->flow_block;
-	struct flow_block_cb *block_cb;
-	int err = 0;
-
-	down_write(&flow_table->flow_block_lock);
-	block_cb = flow_block_cb_lookup(block, cb, cb_priv);
-	if (block_cb) {
-		err = -EEXIST;
-		goto unlock;
-	}
-
-	block_cb = flow_block_cb_alloc(cb, cb_priv, cb_priv, NULL);
-	if (IS_ERR(block_cb)) {
-		err = PTR_ERR(block_cb);
-		goto unlock;
-	}
-
-	list_add_tail(&block_cb->list, &block->cb_list);
-
-unlock:
-	up_write(&flow_table->flow_block_lock);
-	return err;
-}
-EXPORT_SYMBOL_GPL(nf_flow_table_offload_add_cb);
-
-void nf_flow_table_offload_del_cb(struct nf_flowtable *flow_table,
-				  flow_setup_cb_t *cb, void *cb_priv)
-{
-	struct flow_block *block = &flow_table->flow_block;
-	struct flow_block_cb *block_cb;
-
-	down_write(&flow_table->flow_block_lock);
-	block_cb = flow_block_cb_lookup(block, cb, cb_priv);
-	if (block_cb) {
-		list_del(&block_cb->list);
-		flow_block_cb_free(block_cb);
-	} else {
-		WARN_ON(true);
-	}
-	up_write(&flow_table->flow_block_lock);
-}
-EXPORT_SYMBOL_GPL(nf_flow_table_offload_del_cb);
 
 static int nf_flow_nat_port_tcp(struct sk_buff *skb, unsigned int thoff,
 				__be16 port, __be16 new_port)