devlink: expose instance locking and add locked port registering

It should be familiar and beneficial to expose devlink instance
lock to the drivers. This way drivers can block devlink from
calling them during critical sections without breakneck locking.

Add port helpers, port splitting callbacks will be the first
target.

Use 'devl_' prefix for "explicitly locked" API. Initial RFC used
'__devlink' but that's too much typing.

devl_lock_is_held() is not defined without lockdep, which is
the same behavior as lockdep_is_held() itself.

Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 71 insertions, 24 deletions

diff --git a/net/core/devlink.c b/net/core/devlink.c
index fcd9f6d85cf1..769e5f7fa219 100644
--- a/net/core/devlink.c
+++ b/net/core/devlink.c
@@ -225,6 +225,33 @@ struct devlink *__must_check devlink_try_get(struct devlink *devlink)
 	return NULL;
 }
 
+void devl_assert_locked(struct devlink *devlink)
+{
+	lockdep_assert_held(&devlink->lock);
+}
+EXPORT_SYMBOL_GPL(devl_assert_locked);
+
+#ifdef CONFIG_LOCKDEP
+/* For use in conjunction with LOCKDEP only e.g. rcu_dereference_protected() */
+bool devl_lock_is_held(struct devlink *devlink)
+{
+	return lockdep_is_held(&devlink->lock);
+}
+EXPORT_SYMBOL_GPL(devl_lock_is_held);
+#endif
+
+void devl_lock(struct devlink *devlink)
+{
+	mutex_lock(&devlink->lock);
+}
+EXPORT_SYMBOL_GPL(devl_lock);
+
+void devl_unlock(struct devlink *devlink)
+{
+	mutex_unlock(&devlink->lock);
+}
+EXPORT_SYMBOL_GPL(devl_unlock);
+
 static struct devlink *devlink_get_from_attrs(struct net *net,
 					      struct nlattr **attrs)
 {
@@ -9249,6 +9276,32 @@ static void devlink_port_type_warn_cancel(struct devlink_port *devlink_port)
 	cancel_delayed_work_sync(&devlink_port->type_warn_dw);
 }
 
+int devl_port_register(struct devlink *devlink,
+		       struct devlink_port *devlink_port,
+		       unsigned int port_index)
+{
+	lockdep_assert_held(&devlink->lock);
+
+	if (devlink_port_index_exists(devlink, port_index))
+		return -EEXIST;
+
+	WARN_ON(devlink_port->devlink);
+	devlink_port->devlink = devlink;
+	devlink_port->index = port_index;
+	spin_lock_init(&devlink_port->type_lock);
+	INIT_LIST_HEAD(&devlink_port->reporter_list);
+	mutex_init(&devlink_port->reporters_lock);
+	list_add_tail(&devlink_port->list, &devlink->port_list);
+	INIT_LIST_HEAD(&devlink_port->param_list);
+	INIT_LIST_HEAD(&devlink_port->region_list);
+
+	INIT_DELAYED_WORK(&devlink_port->type_warn_dw, &devlink_port_type_warn);
+	devlink_port_type_warn_schedule(devlink_port);
+	devlink_port_notify(devlink_port, DEVLINK_CMD_PORT_NEW);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(devl_port_register);
+
 /**
  *	devlink_port_register - Register devlink port
  *
@@ -9266,29 +9319,28 @@ int devlink_port_register(struct devlink *devlink,
 			  struct devlink_port *devlink_port,
 			  unsigned int port_index)
 {
-	mutex_lock(&devlink->lock);
-	if (devlink_port_index_exists(devlink, port_index)) {
-		mutex_unlock(&devlink->lock);
-		return -EEXIST;
-	}
+	int err;
 
-	WARN_ON(devlink_port->devlink);
-	devlink_port->devlink = devlink;
-	devlink_port->index = port_index;
-	spin_lock_init(&devlink_port->type_lock);
-	INIT_LIST_HEAD(&devlink_port->reporter_list);
-	mutex_init(&devlink_port->reporters_lock);
-	list_add_tail(&devlink_port->list, &devlink->port_list);
-	INIT_LIST_HEAD(&devlink_port->param_list);
-	INIT_LIST_HEAD(&devlink_port->region_list);
+	mutex_lock(&devlink->lock);
+	err = devl_port_register(devlink, devlink_port, port_index);
 	mutex_unlock(&devlink->lock);
-	INIT_DELAYED_WORK(&devlink_port->type_warn_dw, &devlink_port_type_warn);
-	devlink_port_type_warn_schedule(devlink_port);
-	devlink_port_notify(devlink_port, DEVLINK_CMD_PORT_NEW);
-	return 0;
+	return err;
 }
 EXPORT_SYMBOL_GPL(devlink_port_register);
 
+void devl_port_unregister(struct devlink_port *devlink_port)
+{
+	lockdep_assert_held(&devlink_port->devlink->lock);
+
+	devlink_port_type_warn_cancel(devlink_port);
+	devlink_port_notify(devlink_port, DEVLINK_CMD_PORT_DEL);
+	list_del(&devlink_port->list);
+	WARN_ON(!list_empty(&devlink_port->reporter_list));
+	WARN_ON(!list_empty(&devlink_port->region_list));
+	mutex_destroy(&devlink_port->reporters_lock);
+}
+EXPORT_SYMBOL_GPL(devl_port_unregister);
+
 /**
  *	devlink_port_unregister - Unregister devlink port
  *
@@ -9298,14 +9350,9 @@ void devlink_port_unregister(struct devlink_port *devlink_port)
 {
 	struct devlink *devlink = devlink_port->devlink;
 
-	devlink_port_type_warn_cancel(devlink_port);
-	devlink_port_notify(devlink_port, DEVLINK_CMD_PORT_DEL);
 	mutex_lock(&devlink->lock);
-	list_del(&devlink_port->list);
+	devl_port_unregister(devlink_port);
 	mutex_unlock(&devlink->lock);
-	WARN_ON(!list_empty(&devlink_port->reporter_list));
-	WARN_ON(!list_empty(&devlink_port->region_list));
-	mutex_destroy(&devlink_port->reporters_lock);
 }
 EXPORT_SYMBOL_GPL(devlink_port_unregister);