[PATCH v8 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 dev-assoc operation.

Signed-off-by: Wei Wang <weibunny@fb.com>
---
 Documentation/netlink/specs/psp.yaml |  2 +-
 net/psp/psp-nl-gen.c                 |  2 +-
 net/psp/psp-nl-gen.h                 |  3 ++
 net/psp/psp.h                        |  1 +
 net/psp/psp_main.c                   | 70 ++++++++++++++++++++++++++++
 net/psp/psp_nl.c                     |  8 ++++
 6 files changed, 84 insertions(+), 2 deletions(-)

diff --git a/Documentation/netlink/specs/psp.yaml b/Documentation/netlink/specs/psp.yaml
index 336ef19155ff..d7c1fc62de1c 100644
--- a/Documentation/netlink/specs/psp.yaml
+++ b/Documentation/netlink/specs/psp.yaml
@@ -320,7 +320,7 @@ operations:
             - nsid
         reply:
           attributes: []
-        pre: psp-device-get-locked
+        pre: psp-device-get-locked-dev-assoc
         post: psp-device-unlock
     -
       name: dev-disassoc
diff --git a/net/psp/psp-nl-gen.c b/net/psp/psp-nl-gen.c
index 114299c64423..389a8480cc3d 100644
--- a/net/psp/psp-nl-gen.c
+++ b/net/psp/psp-nl-gen.c
@@ -135,7 +135,7 @@ static const struct genl_split_ops psp_nl_ops[] = {
 	},
 	{
 		.cmd		= PSP_CMD_DEV_ASSOC,
-		.pre_doit	= psp_device_get_locked,
+		.pre_doit	= psp_device_get_locked_dev_assoc,
 		.doit		= psp_nl_dev_assoc_doit,
 		.post_doit	= psp_device_unlock,
 		.policy		= psp_dev_assoc_nl_policy,
diff --git a/net/psp/psp-nl-gen.h b/net/psp/psp-nl-gen.h
index 4dd0f0f23053..24d51bff997f 100644
--- a/net/psp/psp-nl-gen.h
+++ b/net/psp/psp-nl-gen.h
@@ -21,6 +21,9 @@ int psp_device_get_locked_admin(const struct genl_split_ops *ops,
 				struct sk_buff *skb, struct genl_info *info);
 int psp_assoc_device_get_locked(const struct genl_split_ops *ops,
 				struct sk_buff *skb, struct genl_info *info);
+int psp_device_get_locked_dev_assoc(const struct genl_split_ops *ops,
+				    struct sk_buff *skb,
+				    struct genl_info *info);
 void
 psp_device_unlock(const struct genl_split_ops *ops, struct sk_buff *skb,
 		  struct genl_info *info);
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..160eaf3e7229 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) {
+		if (!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
--- a/net/psp/psp_nl.c
+++ b/net/psp/psp_nl.c
@@ -159,6 +159,14 @@ int psp_device_get_locked(const struct genl_split_ops *ops,
 	return __psp_device_get_locked(ops, skb, info, false);
 }
 
+int psp_device_get_locked_dev_assoc(const struct genl_split_ops *ops,
+				    struct sk_buff *skb, struct genl_info *info)
+{
+	psp_attach_netdev_notifier();
+
+	return __psp_device_get_locked(ops, skb, info, false);
+}
+
 void
 psp_device_unlock(const struct genl_split_ops *ops, struct sk_buff *skb,
 		  struct genl_info *info)
-- 
2.52.0