[PATCH v6 net-next 3/5] psp: add a new netdev event for dev unregister

[Wei Wang <weibunny.kernel@gmail.com>]

From: Wei Wang <weibunny@fb.com>

Add a new netdev event for dev unregister and handle the removal of this
dev from psp->assoc_dev_list, upon the first successful dev-assoc
operation.

Signed-off-by: Wei Wang <weibunny@fb.com>
---
 net/psp/psp.h      |  1 +
 net/psp/psp_main.c | 70 ++++++++++++++++++++++++++++++++++++++++++++++
 net/psp/psp_nl.c   |  7 +++++
 3 files changed, 78 insertions(+)

diff --git a/net/psp/psp.h b/net/psp/psp.h
index 0f9c4e4e52cb..fd7457dedd30 100644
--- a/net/psp/psp.h
+++ b/net/psp/psp.h
@@ -15,6 +15,7 @@ extern struct mutex psp_devs_lock;
 
 void psp_dev_free(struct psp_dev *psd);
 int psp_dev_check_access(struct psp_dev *psd, struct net *net, bool admin);
+void psp_attach_netdev_notifier(void);
 
 void psp_nl_notify_dev(struct psp_dev *psd, u32 cmd);
 
diff --git a/net/psp/psp_main.c b/net/psp/psp_main.c
index 178b848989f1..db4593e76fa7 100644
--- a/net/psp/psp_main.c
+++ b/net/psp/psp_main.c
@@ -375,10 +375,80 @@ int psp_dev_rcv(struct sk_buff *skb, u16 dev_id, u8 generation, bool strip_icv)
 }
 EXPORT_SYMBOL(psp_dev_rcv);
 
+static void psp_dev_disassoc_one(struct psp_dev *psd, struct net_device *dev)
+{
+	struct psp_assoc_dev *entry, *tmp;
+
+	list_for_each_entry_safe(entry, tmp, &psd->assoc_dev_list, dev_list) {
+		if (entry->assoc_dev == dev) {
+			list_del(&entry->dev_list);
+			rcu_assign_pointer(entry->assoc_dev->psp_dev, NULL);
+			netdev_put(entry->assoc_dev, &entry->dev_tracker);
+			kfree(entry);
+			return;
+		}
+	}
+}
+
+static int psp_netdev_event(struct notifier_block *nb, unsigned long event,
+			    void *ptr)
+{
+	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
+	struct psp_dev *psd;
+
+	if (event != NETDEV_UNREGISTER)
+		return NOTIFY_DONE;
+
+	rcu_read_lock();
+	psd = rcu_dereference(dev->psp_dev);
+	if (psd && psp_dev_tryget(psd)) {
+		rcu_read_unlock();
+		mutex_lock(&psd->lock);
+		psp_dev_disassoc_one(psd, dev);
+		mutex_unlock(&psd->lock);
+		psp_dev_put(psd);
+	} else {
+		rcu_read_unlock();
+	}
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block psp_netdev_notifier = {
+	.notifier_call = psp_netdev_event,
+};
+
+static bool psp_notifier_registered;
+
+/**
+ * psp_attach_netdev_notifier() - register netdev notifier on first use
+ *
+ * Register the netdevice notifier when the first device association
+ * is created. In many installations no associations will be created and
+ * the notifier won't be needed.
+ *
+ * Must be called without psd->lock held, due to lock ordering:
+ * rtnl_lock -> psd->lock (the notifier callback runs under rtnl_lock
+ * and takes psd->lock).
+ */
+void psp_attach_netdev_notifier(void)
+{
+	if (READ_ONCE(psp_notifier_registered))
+		return;
+
+	mutex_lock(&psp_devs_lock);
+	if (!psp_notifier_registered) {
+		register_netdevice_notifier(&psp_netdev_notifier);
+		WRITE_ONCE(psp_notifier_registered, true);
+	}
+	mutex_unlock(&psp_devs_lock);
+}
+
 static int __init psp_init(void)
 {
 	mutex_init(&psp_devs_lock);
 
 	return genl_register_family(&psp_nl_family);
 }
+
 subsys_initcall(psp_init);
diff --git a/net/psp/psp_nl.c b/net/psp/psp_nl.c
index aa60a8277829..44e00add4211 100644
--- a/net/psp/psp_nl.c
+++ b/net/psp/psp_nl.c
@@ -515,6 +515,13 @@ int psp_nl_dev_assoc_doit(struct sk_buff *skb, struct genl_info *info)
 
 	psp_nl_notify_dev(psd, PSP_CMD_DEV_CHANGE_NTF);
 
+	/* Register netdev notifier for assoc cleanup on success.
+	 * Must drop psd->lock to ensure lock ordering: rtnl_lock -> psd->lock
+	 */
+	mutex_unlock(&psd->lock);
+	psp_attach_netdev_notifier();
+	mutex_lock(&psd->lock);
+
 	return psp_nl_reply_send(rsp, info);
 }
 
-- 
2.52.0