[RFC 2/5] devlink: add API for explicit locking

@@ -1191,6 +1191,7 @@ enum {
 };
 
 struct devlink_ops {
+	struct module *owner;
 	/**
 	 * @supported_flash_update_params:
 	 * mask of parameters supported by the driver's .flash_update

@@ -1490,6 +1491,8 @@ void *devlink_priv(struct devlink *devlink);
 struct devlink *priv_to_devlink(void *priv);
 struct device *devlink_to_dev(const struct devlink *devlink);
 
+int lockdep_devlink_is_held(struct devlink *devlink);
+
 struct ib_device;
 
 struct net *devlink_net(const struct devlink *devlink);

@@ -1507,10 +1510,23 @@ static inline struct devlink *devlink_alloc(const struct devlink_ops *ops,
 {
 	return devlink_alloc_ns(ops, priv_size, &init_net, dev);
 }
+
+void devlink_lock(struct devlink *devlink);
+void devlink_unlock(struct devlink *devlink);
+
+void devlink_lock_reg(struct devlink *devlink);
+void devlink_unlock_reg(struct devlink *devlink);
+
+void devlink_get(struct devlink *devlink);
+bool devlink_is_alive(const struct devlink *devlink);
+
 void devlink_set_features(struct devlink *devlink, u64 features);
 void devlink_register(struct devlink *devlink);
+void __devlink_register(struct devlink *devlink);
 void devlink_unregister(struct devlink *devlink);
+void __devlink_unregister(struct devlink *devlink);
 void devlink_free(struct devlink *devlink);
+void __devlink_free(struct devlink *devlink);
 int devlink_port_register(struct devlink *devlink,
 			  struct devlink_port *devlink_port,
 			  unsigned int port_index);

@@ -182,11 +182,24 @@ struct net *devlink_net(const struct devlink *devlink)
 }
 EXPORT_SYMBOL_GPL(devlink_net);
 
+void devlink_free(struct devlink *devlink);
+
 void devlink_put(struct devlink *devlink)
 {
-	if (refcount_dec_and_test(&devlink->refcount))
-		complete(&devlink->comp);
+	if (refcount_dec_and_test(&devlink->refcount)) {
+		if (devlink->ops->lock_flags & DEVLINK_LOCK_REF_MODE)
+			devlink_free(devlink);
+		else
+			complete(&devlink->comp);
+	}
 }
+EXPORT_SYMBOL_GPL(devlink_put);
+
+void devlink_get(struct devlink *devlink)
+{
+	refcount_inc(&devlink->refcount);
+}
+EXPORT_SYMBOL_GPL(devlink_get);
 
 struct devlink *__must_check devlink_try_get(struct devlink *devlink)
 {

@@ -195,6 +208,60 @@ struct devlink *__must_check devlink_try_get(struct devlink *devlink)
 	return NULL;
 }
 
+bool devlink_is_alive(const struct devlink *devlink)
+{
+	return xa_get_mark(&devlinks, devlink->index, DEVLINK_REGISTERED);
+}
+EXPORT_SYMBOL_GPL(devlink_is_alive);
+
+/**
+ * devlink_lock_reg() - take devlink registration lock as well as instance lock
+ * @devlink: instance to lock
+ */
+void devlink_lock_reg(struct devlink *devlink)
+{
+	mutex_lock(&devlink_mutex);
+	mutex_lock(&devlink->lock);
+}
+EXPORT_SYMBOL_GPL(devlink_lock_reg);
+
+/**
+ * devlink_unlock_reg()
+ * @devlink: instance to lock
+ */
+void devlink_unlock_reg(struct devlink *devlink)
+{
+	mutex_unlock(&devlink->lock);
+	mutex_unlock(&devlink_mutex);
+}
+EXPORT_SYMBOL_GPL(devlink_unlock_reg);
+
+/**
+ * devlink_lock() - lock devlink instance
+ * @devlink: instance to lock
+ */
+void devlink_lock(struct devlink *devlink)
+{
+	mutex_lock(&devlink->lock);
+}
+EXPORT_SYMBOL_GPL(devlink_lock);
+
+/**
+ * devlink_unlock() - release devlink instance lock
+ * @devlink: instance to unlock
+ */
+void devlink_unlock(struct devlink *devlink)
+{
+	mutex_unlock(&devlink->lock);
+}
+EXPORT_SYMBOL_GPL(devlink_unlock);
+
+int lockdep_devlink_is_held(struct devlink *devlink)
+{
+	return lockdep_is_held(&devlink->lock);
+}
+EXPORT_SYMBOL_GPL(lockdep_devlink_is_held);
+
 static struct devlink *devlink_get_from_attrs(struct net *net,
 					      struct nlattr **attrs)
 {

@@ -9016,6 +9083,7 @@ struct devlink *devlink_alloc_ns(const struct devlink_ops *ops,
 	mutex_init(&devlink->reporters_lock);
 	refcount_set(&devlink->refcount, 1);
 	init_completion(&devlink->comp);
+	__module_get(devlink->ops->owner);
 
 	return devlink;
 }

@@ -9105,6 +9173,18 @@ static void devlink_notify_unregister(struct devlink *devlink)
 	devlink_notify(devlink, DEVLINK_CMD_DEL);
 }
 
+void __devlink_register(struct devlink *devlink)
+{
+	ASSERT_DEVLINK_NOT_REGISTERED(devlink);
+	lockdep_assert_held(&devlink->lock);
+	lockdep_assert_held(&devlink_mutex);
+	/* Make sure that we are in .probe() routine */
+
+	xa_set_mark(&devlinks, devlink->index, DEVLINK_REGISTERED);
+	devlink_notify_register(devlink);
+}
+EXPORT_SYMBOL_GPL(__devlink_register);
+
 /**
  *	devlink_register - Register devlink instance
  *

@@ -9112,16 +9192,27 @@ static void devlink_notify_unregister(struct devlink *devlink)
  */
 void devlink_register(struct devlink *devlink)
 {
-	ASSERT_DEVLINK_NOT_REGISTERED(devlink);
-	/* Make sure that we are in .probe() routine */
-
 	mutex_lock(&devlink_mutex);
-	xa_set_mark(&devlinks, devlink->index, DEVLINK_REGISTERED);
-	devlink_notify_register(devlink);
+	__devlink_register(devlink);
 	mutex_unlock(&devlink_mutex);
 }
 EXPORT_SYMBOL_GPL(devlink_register);
 
+/* Note: this is NOT an equivalent to devlink_unregister() sans locking
+ * it also accounts for the ability to take references on the instance.
+ */
+void __devlink_unregister(struct devlink *devlink)
+{
+	ASSERT_DEVLINK_REGISTERED(devlink);
+	/* Make sure that we are in .remove() routine */
+	WARN_ON(!(devlink->ops->lock_flags & DEVLINK_LOCK_REF_MODE));
+	lockdep_assert_held(&devlink->lock);
+
+	devlink_notify_unregister(devlink);
+	xa_clear_mark(&devlinks, devlink->index, DEVLINK_REGISTERED);
+}
+EXPORT_SYMBOL_GPL(__devlink_unregister);
+
 /**
  *	devlink_unregister - Unregister devlink instance
  *

@@ -9131,6 +9222,7 @@ void devlink_unregister(struct devlink *devlink)
 {
 	ASSERT_DEVLINK_REGISTERED(devlink);
 	/* Make sure that we are in .remove() routine */
+	WARN_ON(devlink->ops->lock_flags & DEVLINK_LOCK_REF_MODE);
 
 	devlink_put(devlink);
 	wait_for_completion(&devlink->comp);

@@ -9142,6 +9234,12 @@ void devlink_unregister(struct devlink *devlink)
 }
 EXPORT_SYMBOL_GPL(devlink_unregister);
 
+void __devlink_free(struct devlink *devlink)
+{
+	devlink_put(devlink);
+}
+EXPORT_SYMBOL_GPL(__devlink_free);
+
 /**
  *	devlink_free - Free devlink instance resources
  *

@@ -9168,6 +9266,8 @@ void devlink_free(struct devlink *devlink)
 	xa_destroy(&devlink->snapshot_ids);
 	xa_erase(&devlinks, devlink->index);
 
+	module_put(devlink->ops->owner);
+
 	kfree(devlink);
 }
 EXPORT_SYMBOL_GPL(devlink_free);

@@ -11502,7 +11602,8 @@ void devlink_compat_running_version(struct devlink *devlink,
 		return;
 
 	mutex_lock(&devlink->lock);
-	__devlink_compat_running_version(devlink, buf, len);
+	if (devlink_is_alive(devlink))
+		__devlink_compat_running_version(devlink, buf, len);
 	mutex_unlock(&devlink->lock);
 }
 

@@ -11519,9 +11620,14 @@ int devlink_compat_flash_update(struct devlink *devlink, const char *file_name)
 		return ret;
 
 	mutex_lock(&devlink->lock);
+	if (!devlink_is_alive(devlink)) {
+		ret = -ENODEV;
+		goto exit_unlock;
+	}
 	devlink_flash_update_begin_notify(devlink);
 	ret = devlink->ops->flash_update(devlink, &params, NULL);
 	devlink_flash_update_end_notify(devlink);
+exit_unlock:
 	mutex_unlock(&devlink->lock);
 
 	release_firmware(params.fw);