Merge branch 'switchdev-blocking-notifiers'

Petr Machata says:

====================
switchdev: Convert switchdev_port_obj_{add,del}() to notifiers

An offloading driver may need to have access to switchdev events on
ports that aren't directly under its control. An example is a VXLAN port
attached to a bridge offloaded by a driver. The driver needs to know
about VLANs configured on the VXLAN device. However the VXLAN device
isn't stashed between the bridge and a front-panel-port device (such as
is the case e.g. for LAG devices), so the usual switchdev ops don't
reach the driver.

VXLAN is likely not the only device type like this: in theory any L2
tunnel device that needs offloading will prompt requirement of this
sort.

A way to fix this is to give up the notion of port object addition /
deletion as a switchdev operation, which assumes somewhat tight coupling
between the message producer and consumer. And instead send the message
over a notifier chain.

The series starts with a clean-up patch #1, where
SWITCHDEV_OBJ_PORT_{VLAN, MDB}() are fixed up to lift the constraint
that the passed-in argument be a simple variable named "obj".

switchdev_port_obj_add and _del are invoked in a context that permits
blocking. Not only that, at least for the VLAN notification, being able
to signal failure is actually important. Therefore introduce a new
blocking notifier chain that the new events will be sent on. That's done
in patch #2. Retain the current (atomic) notifier chain for the
preexisting notifications.

In patch #3, introduce two new switchdev notifier types,
SWITCHDEV_PORT_OBJ_ADD and SWITCHDEV_PORT_OBJ_DEL. These notifier types
communicate the same event as the corresponding switchdev op, except in
a form of a notification. struct switchdev_notifier_port_obj_info was
added to carry the fields that correspond to the switchdev op arguments.
An additional field, handled, will be used to communicate back to
switchdev that the event has reached an interested party, which will be
important for the two-phase commit.

In patches #4, #5, and #7, rocker, DSA resp. ethsw are updated to
subscribe to the switchdev blocking notifier chain, and handle the new
notifier types. #6 introduces a helper to determine whether a
netdevice corresponds to a front panel port.

What these three drivers have in common is that their ports don't
support any uppers besides bridge. That makes it possible to ignore any
notifiers that don't reference a front-panel port device, because they
are certainly out of scope.

Unlike the previous three, mlxsw and ocelot drivers admit stacked
devices as uppers. While the current switchdev code recursively descends
through layers of lower devices, eventually calling the op on a
front-panel port device, the notifier would reference a stacking device
that's one of front-panel ports uppers. The filtering is thus more
complex.

For ocelot, such iteration is currently pretty much required, because
there's no bookkeeping of LAG devices. mlxsw does keep the list of LAGs,
however it iterates the lower devices anyway when deciding whether an
event on a tunnel device pertains to the driver or not.

Therefore this patch set instead introduces, in patch #8, a helper to
iterate through lowers, much like the current switchdev code does,
looking for devices that match a given predicate.

Then in patches #9 and #10, first mlxsw and then ocelot are updated to
dispatch the newly-added notifier types to the preexisting
port_obj_add/_del handlers. The dispatch is done via the new helper, to
recursively descend through lower devices.

Finally in patch #11, the actual switch is made, retiring the current
SDO-based code in favor of a notifier.

Now that the event is distributed through a notifier, the explicit
netdevice check in rocker, DSA and ethsw doesn't let through any events
except those done on a front-panel port itself. It is therefore
unnecessary to check in VLAN-handling code whether a VLAN was added to
the bridge itself: such events will simply be ignored much sooner.
Therefore remove it in patch #12.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 151 insertions, 42 deletions

diff --git a/net/switchdev/switchdev.c b/net/switchdev/switchdev.c
index 74b9d916a58b..fe23fac4dc4b 100644
--- a/net/switchdev/switchdev.c
+++ b/net/switchdev/switchdev.c
@@ -353,30 +353,29 @@ static size_t switchdev_obj_size(const struct switchdev_obj *obj)
 	return 0;
 }
 
-static int __switchdev_port_obj_add(struct net_device *dev,
-				    const struct switchdev_obj *obj,
-				    struct switchdev_trans *trans)
+static int switchdev_port_obj_notify(enum switchdev_notifier_type nt,
+				     struct net_device *dev,
+				     const struct switchdev_obj *obj,
+				     struct switchdev_trans *trans)
 {
-	const struct switchdev_ops *ops = dev->switchdev_ops;
-	struct net_device *lower_dev;
-	struct list_head *iter;
-	int err = -EOPNOTSUPP;
-
-	if (ops && ops->switchdev_port_obj_add)
-		return ops->switchdev_port_obj_add(dev, obj, trans);
+	int rc;
+	int err;
 
-	/* Switch device port(s) may be stacked under
-	 * bond/team/vlan dev, so recurse down to add object on
-	 * each port.
-	 */
+	struct switchdev_notifier_port_obj_info obj_info = {
+		.obj = obj,
+		.trans = trans,
+		.handled = false,
+	};
 
-	netdev_for_each_lower_dev(dev, lower_dev, iter) {
-		err = __switchdev_port_obj_add(lower_dev, obj, trans);
-		if (err)
-			break;
+	rc = call_switchdev_blocking_notifiers(nt, dev, &obj_info.info);
+	err = notifier_to_errno(rc);
+	if (err) {
+		WARN_ON(!obj_info.handled);
+		return err;
 	}
-
-	return err;
+	if (!obj_info.handled)
+		return -EOPNOTSUPP;
+	return 0;
 }
 
 static int switchdev_port_obj_add_now(struct net_device *dev,
@@ -397,7 +396,8 @@ static int switchdev_port_obj_add_now(struct net_device *dev,
 	 */
 
 	trans.ph_prepare = true;
-	err = __switchdev_port_obj_add(dev, obj, &trans);
+	err = switchdev_port_obj_notify(SWITCHDEV_PORT_OBJ_ADD,
+					dev, obj, &trans);
 	if (err) {
 		/* Prepare phase failed: abort the transaction.  Any
 		 * resources reserved in the prepare phase are
@@ -416,7 +416,8 @@ static int switchdev_port_obj_add_now(struct net_device *dev,
 	 */
 
 	trans.ph_prepare = false;
-	err = __switchdev_port_obj_add(dev, obj, &trans);
+	err = switchdev_port_obj_notify(SWITCHDEV_PORT_OBJ_ADD,
+					dev, obj, &trans);
 	WARN(err, "%s: Commit of object (id=%d) failed.\n", dev->name, obj->id);
 	switchdev_trans_items_warn_destroy(dev, &trans);
 
@@ -471,26 +472,8 @@ EXPORT_SYMBOL_GPL(switchdev_port_obj_add);
 static int switchdev_port_obj_del_now(struct net_device *dev,
 				      const struct switchdev_obj *obj)
 {
-	const struct switchdev_ops *ops = dev->switchdev_ops;
-	struct net_device *lower_dev;
-	struct list_head *iter;
-	int err = -EOPNOTSUPP;
-
-	if (ops && ops->switchdev_port_obj_del)
-		return ops->switchdev_port_obj_del(dev, obj);
-
-	/* Switch device port(s) may be stacked under
-	 * bond/team/vlan dev, so recurse down to delete object on
-	 * each port.
-	 */
-
-	netdev_for_each_lower_dev(dev, lower_dev, iter) {
-		err = switchdev_port_obj_del_now(lower_dev, obj);
-		if (err)
-			break;
-	}
-
-	return err;
+	return switchdev_port_obj_notify(SWITCHDEV_PORT_OBJ_DEL,
+					 dev, obj, NULL);
 }
 
 static void switchdev_port_obj_del_deferred(struct net_device *dev,
@@ -535,6 +518,7 @@ int switchdev_port_obj_del(struct net_device *dev,
 EXPORT_SYMBOL_GPL(switchdev_port_obj_del);
 
 static ATOMIC_NOTIFIER_HEAD(switchdev_notif_chain);
+static BLOCKING_NOTIFIER_HEAD(switchdev_blocking_notif_chain);
 
 /**
  *	register_switchdev_notifier - Register notifier
@@ -576,6 +560,31 @@ int call_switchdev_notifiers(unsigned long val, struct net_device *dev,
 }
 EXPORT_SYMBOL_GPL(call_switchdev_notifiers);
 
+int register_switchdev_blocking_notifier(struct notifier_block *nb)
+{
+	struct blocking_notifier_head *chain = &switchdev_blocking_notif_chain;
+
+	return blocking_notifier_chain_register(chain, nb);
+}
+EXPORT_SYMBOL_GPL(register_switchdev_blocking_notifier);
+
+int unregister_switchdev_blocking_notifier(struct notifier_block *nb)
+{
+	struct blocking_notifier_head *chain = &switchdev_blocking_notif_chain;
+
+	return blocking_notifier_chain_unregister(chain, nb);
+}
+EXPORT_SYMBOL_GPL(unregister_switchdev_blocking_notifier);
+
+int call_switchdev_blocking_notifiers(unsigned long val, struct net_device *dev,
+				      struct switchdev_notifier_info *info)
+{
+	info->dev = dev;
+	return blocking_notifier_call_chain(&switchdev_blocking_notif_chain,
+					    val, info);
+}
+EXPORT_SYMBOL_GPL(call_switchdev_blocking_notifiers);
+
 bool switchdev_port_same_parent_id(struct net_device *a,
 				   struct net_device *b)
 {
@@ -595,3 +604,103 @@ bool switchdev_port_same_parent_id(struct net_device *a,
 	return netdev_phys_item_id_same(&a_attr.u.ppid, &b_attr.u.ppid);
 }
 EXPORT_SYMBOL_GPL(switchdev_port_same_parent_id);
+
+static int __switchdev_handle_port_obj_add(struct net_device *dev,
+			struct switchdev_notifier_port_obj_info *port_obj_info,
+			bool (*check_cb)(const struct net_device *dev),
+			int (*add_cb)(struct net_device *dev,
+				      const struct switchdev_obj *obj,
+				      struct switchdev_trans *trans))
+{
+	struct net_device *lower_dev;
+	struct list_head *iter;
+	int err = -EOPNOTSUPP;
+
+	if (check_cb(dev)) {
+		/* This flag is only checked if the return value is success. */
+		port_obj_info->handled = true;
+		return add_cb(dev, port_obj_info->obj, port_obj_info->trans);
+	}
+
+	/* Switch ports might be stacked under e.g. a LAG. Ignore the
+	 * unsupported devices, another driver might be able to handle them. But
+	 * propagate to the callers any hard errors.
+	 *
+	 * If the driver does its own bookkeeping of stacked ports, it's not
+	 * necessary to go through this helper.
+	 */
+	netdev_for_each_lower_dev(dev, lower_dev, iter) {
+		err = __switchdev_handle_port_obj_add(lower_dev, port_obj_info,
+						      check_cb, add_cb);
+		if (err && err != -EOPNOTSUPP)
+			return err;
+	}
+
+	return err;
+}
+
+int switchdev_handle_port_obj_add(struct net_device *dev,
+			struct switchdev_notifier_port_obj_info *port_obj_info,
+			bool (*check_cb)(const struct net_device *dev),
+			int (*add_cb)(struct net_device *dev,
+				      const struct switchdev_obj *obj,
+				      struct switchdev_trans *trans))
+{
+	int err;
+
+	err = __switchdev_handle_port_obj_add(dev, port_obj_info, check_cb,
+					      add_cb);
+	if (err == -EOPNOTSUPP)
+		err = 0;
+	return err;
+}
+EXPORT_SYMBOL_GPL(switchdev_handle_port_obj_add);
+
+static int __switchdev_handle_port_obj_del(struct net_device *dev,
+			struct switchdev_notifier_port_obj_info *port_obj_info,
+			bool (*check_cb)(const struct net_device *dev),
+			int (*del_cb)(struct net_device *dev,
+				      const struct switchdev_obj *obj))
+{
+	struct net_device *lower_dev;
+	struct list_head *iter;
+	int err = -EOPNOTSUPP;
+
+	if (check_cb(dev)) {
+		/* This flag is only checked if the return value is success. */
+		port_obj_info->handled = true;
+		return del_cb(dev, port_obj_info->obj);
+	}
+
+	/* Switch ports might be stacked under e.g. a LAG. Ignore the
+	 * unsupported devices, another driver might be able to handle them. But
+	 * propagate to the callers any hard errors.
+	 *
+	 * If the driver does its own bookkeeping of stacked ports, it's not
+	 * necessary to go through this helper.
+	 */
+	netdev_for_each_lower_dev(dev, lower_dev, iter) {
+		err = __switchdev_handle_port_obj_del(lower_dev, port_obj_info,
+						      check_cb, del_cb);
+		if (err && err != -EOPNOTSUPP)
+			return err;
+	}
+
+	return err;
+}
+
+int switchdev_handle_port_obj_del(struct net_device *dev,
+			struct switchdev_notifier_port_obj_info *port_obj_info,
+			bool (*check_cb)(const struct net_device *dev),
+			int (*del_cb)(struct net_device *dev,
+				      const struct switchdev_obj *obj))
+{
+	int err;
+
+	err = __switchdev_handle_port_obj_del(dev, port_obj_info, check_cb,
+					      del_cb);
+	if (err == -EOPNOTSUPP)
+		err = 0;
+	return err;
+}
+EXPORT_SYMBOL_GPL(switchdev_handle_port_obj_del);