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, 38 insertions, 32 deletions

diff --git a/net/dsa/port.c b/net/dsa/port.c
index f6ea41cbcdd5..fbf2d7fc5c91 100644
--- a/net/dsa/port.c
+++ b/net/dsa/port.c
@@ -130,7 +130,7 @@ int dsa_port_enable_rt(struct dsa_port *dp, struct phy_device *phy)
 			return err;
 	}
 
-	if (!dp->bridge_dev)
+	if (!dp->bridge)
 		dsa_port_set_state_now(dp, BR_STATE_FORWARDING, false);
 
 	if (dp->pl)
@@ -158,7 +158,7 @@ void dsa_port_disable_rt(struct dsa_port *dp)
 	if (dp->pl)
 		phylink_stop(dp->pl);
 
-	if (!dp->bridge_dev)
+	if (!dp->bridge)
 		dsa_port_set_state_now(dp, BR_STATE_DISABLED, false);
 
 	if (ds->ops->port_disable)
@@ -271,36 +271,32 @@ static void dsa_port_switchdev_unsync_attrs(struct dsa_port *dp)
 }
 
 static void dsa_port_bridge_tx_fwd_unoffload(struct dsa_port *dp,
-					     struct net_device *bridge_dev,
-					     unsigned int bridge_num)
+					     struct dsa_bridge bridge)
 {
 	struct dsa_switch *ds = dp->ds;
 
 	/* No bridge TX forwarding offload => do nothing */
-	if (!ds->ops->port_bridge_tx_fwd_unoffload || !bridge_num)
+	if (!ds->ops->port_bridge_tx_fwd_unoffload || !bridge.num)
 		return;
 
 	/* Notify the chips only once the offload has been deactivated, so
 	 * that they can update their configuration accordingly.
 	 */
-	ds->ops->port_bridge_tx_fwd_unoffload(ds, dp->index, bridge_dev,
-					      bridge_num);
+	ds->ops->port_bridge_tx_fwd_unoffload(ds, dp->index, bridge);
 }
 
 static bool dsa_port_bridge_tx_fwd_offload(struct dsa_port *dp,
-					   struct net_device *bridge_dev,
-					   unsigned int bridge_num)
+					   struct dsa_bridge bridge)
 {
 	struct dsa_switch *ds = dp->ds;
 	int err;
 
 	/* FDB isolation is required for TX forwarding offload */
-	if (!ds->ops->port_bridge_tx_fwd_offload || !bridge_num)
+	if (!ds->ops->port_bridge_tx_fwd_offload || !bridge.num)
 		return false;
 
 	/* Notify the driver */
-	err = ds->ops->port_bridge_tx_fwd_offload(ds, dp->index, bridge_dev,
-						  bridge_num);
+	err = ds->ops->port_bridge_tx_fwd_offload(ds, dp->index, bridge);
 
 	return err ? false : true;
 }
@@ -310,21 +306,32 @@ static int dsa_port_bridge_create(struct dsa_port *dp,
 				  struct netlink_ext_ack *extack)
 {
 	struct dsa_switch *ds = dp->ds;
-	unsigned int bridge_num;
+	struct dsa_bridge *bridge;
 
-	dp->bridge_dev = br;
-
-	if (!ds->max_num_bridges)
+	bridge = dsa_tree_bridge_find(ds->dst, br);
+	if (bridge) {
+		refcount_inc(&bridge->refcount);
+		dp->bridge = bridge;
 		return 0;
+	}
+
+	bridge = kzalloc(sizeof(*bridge), GFP_KERNEL);
+	if (!bridge)
+		return -ENOMEM;
+
+	refcount_set(&bridge->refcount, 1);
+
+	bridge->dev = br;
 
-	bridge_num = dsa_bridge_num_get(br, ds->max_num_bridges);
-	if (!bridge_num) {
+	bridge->num = dsa_bridge_num_get(br, ds->max_num_bridges);
+	if (ds->max_num_bridges && !bridge->num) {
 		NL_SET_ERR_MSG_MOD(extack,
 				   "Range of offloadable bridges exceeded");
+		kfree(bridge);
 		return -EOPNOTSUPP;
 	}
 
-	dp->bridge_num = bridge_num;
+	dp->bridge = bridge;
 
 	return 0;
 }
@@ -332,16 +339,17 @@ static int dsa_port_bridge_create(struct dsa_port *dp,
 static void dsa_port_bridge_destroy(struct dsa_port *dp,
 				    const struct net_device *br)
 {
-	struct dsa_switch *ds = dp->ds;
+	struct dsa_bridge *bridge = dp->bridge;
+
+	dp->bridge = NULL;
 
-	dp->bridge_dev = NULL;
+	if (!refcount_dec_and_test(&bridge->refcount))
+		return;
 
-	if (ds->max_num_bridges) {
-		int bridge_num = dp->bridge_num;
+	if (bridge->num)
+		dsa_bridge_num_put(br, bridge->num);
 
-		dp->bridge_num = 0;
-		dsa_bridge_num_put(br, bridge_num);
-	}
+	kfree(bridge);
 }
 
 int dsa_port_bridge_join(struct dsa_port *dp, struct net_device *br,
@@ -351,7 +359,6 @@ int dsa_port_bridge_join(struct dsa_port *dp, struct net_device *br,
 		.tree_index = dp->ds->dst->index,
 		.sw_index = dp->ds->index,
 		.port = dp->index,
-		.br = br,
 	};
 	struct net_device *dev = dp->slave;
 	struct net_device *brport_dev;
@@ -367,12 +374,12 @@ int dsa_port_bridge_join(struct dsa_port *dp, struct net_device *br,
 
 	brport_dev = dsa_port_to_bridge_port(dp);
 
+	info.bridge = *dp->bridge;
 	err = dsa_broadcast(DSA_NOTIFIER_BRIDGE_JOIN, &info);
 	if (err)
 		goto out_rollback;
 
-	tx_fwd_offload = dsa_port_bridge_tx_fwd_offload(dp, br,
-							dsa_port_bridge_num_get(dp));
+	tx_fwd_offload = dsa_port_bridge_tx_fwd_offload(dp, info.bridge);
 
 	err = switchdev_bridge_port_offload(brport_dev, dev, dp,
 					    &dsa_slave_switchdev_notifier,
@@ -415,12 +422,11 @@ void dsa_port_pre_bridge_leave(struct dsa_port *dp, struct net_device *br)
 
 void dsa_port_bridge_leave(struct dsa_port *dp, struct net_device *br)
 {
-	unsigned int bridge_num = dsa_port_bridge_num_get(dp);
 	struct dsa_notifier_bridge_info info = {
 		.tree_index = dp->ds->dst->index,
 		.sw_index = dp->ds->index,
 		.port = dp->index,
-		.br = br,
+		.bridge = *dp->bridge,
 	};
 	int err;
 
@@ -429,7 +435,7 @@ void dsa_port_bridge_leave(struct dsa_port *dp, struct net_device *br)
 	 */
 	dsa_port_bridge_destroy(dp, br);
 
-	dsa_port_bridge_tx_fwd_unoffload(dp, br, bridge_num);
+	dsa_port_bridge_tx_fwd_unoffload(dp, info.bridge);
 
 	err = dsa_broadcast(DSA_NOTIFIER_BRIDGE_LEAVE, &info);
 	if (err)