net: flow_offload: add flow_block_cb_is_busy() and use it

This patch adds a function to check if flow block callback is already in
use.  Call this new function from flow_block_cb_setup_simple() and from
drivers.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlx5/core/en_rep.c

@@ -722,6 +722,10 @@ mlx5e_rep_indr_setup_tc_block(struct net_device *netdev,
 		if (indr_priv)
 			return -EEXIST;
 
+		if (flow_block_cb_is_busy(mlx5e_rep_indr_setup_block_cb,
+					  indr_priv, &mlx5e_block_cb_list))
+			return -EBUSY;
+
 		indr_priv = kmalloc(sizeof(*indr_priv), GFP_KERNEL);
 		if (!indr_priv)
 			return -ENOMEM;

drivers/net/ethernet/mellanox/mlxsw/spectrum.c

@@ -1698,6 +1698,10 @@ static int mlxsw_sp_setup_tc_block(struct mlxsw_sp_port *mlxsw_sp_port,
 
 	switch (f->command) {
 	case FLOW_BLOCK_BIND:
+		if (flow_block_cb_is_busy(cb, mlxsw_sp_port,
+					  &mlxsw_sp_block_cb_list))
+			return -EBUSY;
+
 		block_cb = flow_block_cb_alloc(f->net, cb, mlxsw_sp_port,
 					       mlxsw_sp_port, NULL);
 		if (IS_ERR(block_cb))

drivers/net/ethernet/mscc/ocelot_tc.c

@@ -153,6 +153,9 @@ static int ocelot_setup_tc_block(struct ocelot_port *port,
 
 	switch (f->command) {
 	case FLOW_BLOCK_BIND:
+		if (flow_block_cb_is_busy(cb, port, &ocelot_block_cb_list))
+			return -EBUSY;
+
 		block_cb = flow_block_cb_alloc(f->net, cb, port, port, NULL);
 		if (IS_ERR(block_cb))
 			return PTR_ERR(block_cb);

drivers/net/ethernet/netronome/nfp/flower/offload.c

@@ -1320,6 +1320,10 @@ static int nfp_flower_setup_tc_block(struct net_device *netdev,
 
 	switch (f->command) {
 	case FLOW_BLOCK_BIND:
+		if (flow_block_cb_is_busy(nfp_flower_setup_tc_block_cb, repr,
+					  &nfp_block_cb_list))
+			return -EBUSY;
+
 		block_cb = flow_block_cb_alloc(f->net,
 					       nfp_flower_setup_tc_block_cb,
 					       repr, repr, NULL);