netdev - [PATCH net 1/2] net: switchdev: Add helper to check if an object event is pending

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Message-Id: <20240131123544.462597-2-tobias@waldekranz.com>
Date: Wed, 31 Jan 2024 13:35:43 +0100
From: Tobias Waldekranz <tobias@...dekranz.com>
To: davem@...emloft.net,
	kuba@...nel.org
Cc: olteanv@...il.com,
	roopa@...dia.com,
	razor@...ckwall.org,
	bridge@...ts.linux.dev,
	netdev@...r.kernel.org,
	jiri@...nulli.us,
	ivecera@...hat.com
Subject: [PATCH net 1/2] net: switchdev: Add helper to check if an object event is pending

When adding/removing a port to/from a bridge, the port must be brought
up to speed with the current state of the bridge. This is done by
replaying all relevant events, directly to the port in question.

In some situations, specifically when replaying the MDB, this process
may race against new events that are generated concurrently. So the
bridge must ensure that the event is not already pending on the
deferred queue. switchdev_port_obj_is_deferred answers this question.

Signed-off-by: Tobias Waldekranz <tobias@...dekranz.com>
---
 include/net/switchdev.h   |  3 ++
 net/switchdev/switchdev.c | 61 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 64 insertions(+)

diff --git a/include/net/switchdev.h b/include/net/switchdev.h
index a43062d4c734..538851a93d9e 100644
--- a/include/net/switchdev.h
+++ b/include/net/switchdev.h
@@ -308,6 +308,9 @@ void switchdev_deferred_process(void);
 int switchdev_port_attr_set(struct net_device *dev,
 			    const struct switchdev_attr *attr,
 			    struct netlink_ext_ack *extack);
+bool switchdev_port_obj_is_deferred(struct net_device *dev,
+				    enum switchdev_notifier_type nt,
+				    const struct switchdev_obj *obj);
 int switchdev_port_obj_add(struct net_device *dev,
 			   const struct switchdev_obj *obj,
 			   struct netlink_ext_ack *extack);
diff --git a/net/switchdev/switchdev.c b/net/switchdev/switchdev.c
index 5b045284849e..40bb17c7fdbf 100644
--- a/net/switchdev/switchdev.c
+++ b/net/switchdev/switchdev.c
@@ -19,6 +19,35 @@
 #include <linux/rtnetlink.h>
 #include <net/switchdev.h>
 
+static bool switchdev_obj_eq(const struct switchdev_obj *a,
+			     const struct switchdev_obj *b)
+{
+	const struct switchdev_obj_port_vlan *va, *vb;
+	const struct switchdev_obj_port_mdb *ma, *mb;
+
+	if (a->id != b->id || a->orig_dev != b->orig_dev)
+		return false;
+
+	switch (a->id) {
+	case SWITCHDEV_OBJ_ID_PORT_VLAN:
+		va = SWITCHDEV_OBJ_PORT_VLAN(a);
+		vb = SWITCHDEV_OBJ_PORT_VLAN(b);
+		return va->flags == vb->flags &&
+			va->vid == vb->vid &&
+			va->changed == vb->changed;
+	case SWITCHDEV_OBJ_ID_PORT_MDB:
+	case SWITCHDEV_OBJ_ID_HOST_MDB:
+		ma = SWITCHDEV_OBJ_PORT_MDB(a);
+		mb = SWITCHDEV_OBJ_PORT_MDB(b);
+		return ma->vid == mb->vid &&
+			!memcmp(ma->addr, mb->addr, sizeof(ma->addr));
+	default:
+		break;
+	}
+
+	BUG();
+}
+
 static LIST_HEAD(deferred);
 static DEFINE_SPINLOCK(deferred_lock);
 
@@ -307,6 +336,38 @@ int switchdev_port_obj_del(struct net_device *dev,
 }
 EXPORT_SYMBOL_GPL(switchdev_port_obj_del);
 
+bool switchdev_port_obj_is_deferred(struct net_device *dev,
+				    enum switchdev_notifier_type nt,
+				    const struct switchdev_obj *obj)
+{
+	struct switchdev_deferred_item *dfitem;
+	bool found = false;
+
+	ASSERT_RTNL();
+
+	spin_lock_bh(&deferred_lock);
+
+	list_for_each_entry(dfitem, &deferred, list) {
+		if (dfitem->dev != dev)
+			continue;
+
+		if ((dfitem->func == switchdev_port_obj_add_deferred &&
+		     nt == SWITCHDEV_PORT_OBJ_ADD) ||
+		    (dfitem->func == switchdev_port_obj_del_deferred &&
+		     nt == SWITCHDEV_PORT_OBJ_DEL)) {
+			if (switchdev_obj_eq((const void *)dfitem->data, obj)) {
+				found = true;
+				break;
+			}
+		}
+	}
+
+	spin_unlock_bh(&deferred_lock);
+
+	return found;
+}
+EXPORT_SYMBOL_GPL(switchdev_port_obj_is_deferred);
+
 static ATOMIC_NOTIFIER_HEAD(switchdev_notif_chain);
 static BLOCKING_NOTIFIER_HEAD(switchdev_blocking_notif_chain);
 
-- 
2.34.1