net: dsa: keep the bridge_dev and bridge_num as part of the same structure

The main desire behind this is to provide coherent bridge information to
the fast path without locking.

For example, right now we set dp->bridge_dev and dp->bridge_num from
separate code paths, it is theoretically possible for a packet
transmission to read these two port properties consecutively and find a
bridge number which does not correspond with the bridge device.

Another desire is to start passing more complex bridge information to
dsa_switch_ops functions. For example, with FDB isolation, it is
expected that drivers will need to be passed the bridge which requested
an FDB/MDB entry to be offloaded, and along with that bridge_dev, the
associated bridge_num should be passed too, in case the driver might
want to implement an isolation scheme based on that number.

We already pass the {bridge_dev, bridge_num} pair to the TX forwarding
offload switch API, however we'd like to remove that and squash it into
the basic bridge join/leave API. So that means we need to pass this
pair to the bridge join/leave API.

During dsa_port_bridge_leave, first we unset dp->bridge_dev, then we
call the driver's .port_bridge_leave with what used to be our
dp->bridge_dev, but provided as an argument.

When bridge_dev and bridge_num get folded into a single structure, we
need to preserve this behavior in dsa_port_bridge_leave: we need a copy
of what used to be in dp->bridge.

Switch drivers check bridge membership by comparing dp->bridge_dev with
the provided bridge_dev, but now, if we provide the struct dsa_bridge as
a pointer, they cannot keep comparing dp->bridge to the provided
pointer, since this only points to an on-stack copy. To make this
obvious and prevent driver writers from forgetting and doing stupid
things, in this new API, the struct dsa_bridge is provided as a full
structure (not very large, contains an int and a pointer) instead of a
pointer. An explicit comparison function needs to be used to determine
bridge membership: dsa_port_offloads_bridge().

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Alvin Šipraga <alsi@bang-olufsen.dk>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 21 insertions, 13 deletions

diff --git a/include/net/dsa.h b/include/net/dsa.h
index 899e13d56fc2..b9789c0cd5e3 100644
--- a/include/net/dsa.h
+++ b/include/net/dsa.h
@@ -219,6 +219,11 @@ struct dsa_mall_tc_entry {
 	};
 };
 
+struct dsa_bridge {
+	struct net_device *dev;
+	unsigned int num;
+	refcount_t refcount;
+};
 
 struct dsa_port {
 	/* A CPU port is physically connected to a master device.
@@ -256,8 +261,7 @@ struct dsa_port {
 	/* Managed by DSA on user ports and by drivers on CPU and DSA ports */
 	bool			learning;
 	u8			stp_state;
-	struct net_device	*bridge_dev;
-	unsigned int		bridge_num;
+	struct dsa_bridge	*bridge;
 	struct devlink_port	devlink_port;
 	bool			devlink_port_setup;
 	struct phylink		*pl;
@@ -588,7 +592,7 @@ static inline bool dsa_port_is_vlan_filtering(const struct dsa_port *dp)
 static inline
 struct net_device *dsa_port_to_bridge_port(const struct dsa_port *dp)
 {
-	if (!dp->bridge_dev)
+	if (!dp->bridge)
 		return NULL;
 
 	if (dp->lag_dev)
@@ -602,12 +606,12 @@ struct net_device *dsa_port_to_bridge_port(const struct dsa_port *dp)
 static inline struct net_device *
 dsa_port_bridge_dev_get(const struct dsa_port *dp)
 {
-	return dp->bridge_dev;
+	return dp->bridge ? dp->bridge->dev : NULL;
 }
 
 static inline unsigned int dsa_port_bridge_num_get(struct dsa_port *dp)
 {
-	return dp->bridge_num;
+	return dp->bridge ? dp->bridge->num : 0;
 }
 
 static inline bool dsa_port_bridge_same(const struct dsa_port *a,
@@ -636,6 +640,12 @@ dsa_port_offloads_bridge_dev(struct dsa_port *dp,
 	return dsa_port_bridge_dev_get(dp) == bridge_dev;
 }
 
+static inline bool dsa_port_offloads_bridge(struct dsa_port *dp,
+					    const struct dsa_bridge *bridge)
+{
+	return dsa_port_bridge_dev_get(dp) == bridge->dev;
+}
+
 /* Returns true if any port of this tree offloads the given net_device */
 static inline bool dsa_tree_offloads_bridge_port(struct dsa_switch_tree *dst,
 						 const struct net_device *dev)
@@ -812,17 +822,15 @@ struct dsa_switch_ops {
 	 */
 	int	(*set_ageing_time)(struct dsa_switch *ds, unsigned int msecs);
 	int	(*port_bridge_join)(struct dsa_switch *ds, int port,
-				    struct net_device *bridge);
+				    struct dsa_bridge bridge);
 	void	(*port_bridge_leave)(struct dsa_switch *ds, int port,
-				     struct net_device *bridge);
+				     struct dsa_bridge bridge);
 	/* Called right after .port_bridge_join() */
 	int	(*port_bridge_tx_fwd_offload)(struct dsa_switch *ds, int port,
-					      struct net_device *bridge,
-					      unsigned int bridge_num);
+					      struct dsa_bridge bridge);
 	/* Called right before .port_bridge_leave() */
 	void	(*port_bridge_tx_fwd_unoffload)(struct dsa_switch *ds, int port,
-						struct net_device *bridge,
-						unsigned int bridge_num);
+						struct dsa_bridge bridge);
 	void	(*port_stp_state_set)(struct dsa_switch *ds, int port,
 				      u8 state);
 	void	(*port_fast_age)(struct dsa_switch *ds, int port);
@@ -894,10 +902,10 @@ struct dsa_switch_ops {
 	 */
 	int	(*crosschip_bridge_join)(struct dsa_switch *ds, int tree_index,
 					 int sw_index, int port,
-					 struct net_device *br);
+					 struct dsa_bridge bridge);
 	void	(*crosschip_bridge_leave)(struct dsa_switch *ds, int tree_index,
 					  int sw_index, int port,
-					  struct net_device *br);
+					  struct dsa_bridge bridge);
 	int	(*crosschip_lag_change)(struct dsa_switch *ds, int sw_index,
 					int port);
 	int	(*crosschip_lag_join)(struct dsa_switch *ds, int sw_index,