[RFT net-next 1/6] devlink: expose instance locking and add locked port registering

[Jakub Kicinski <kuba@kernel.org>]

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.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 include/net/devlink.h | 11 +++++
 net/core/devlink.c    | 99 ++++++++++++++++++++++++++++++++-----------
 2 files changed, 86 insertions(+), 24 deletions(-)

diff --git a/include/net/devlink.h b/include/net/devlink.h
index 8d5349d2fb68..9de0d091aee9 100644
--- a/include/net/devlink.h
+++ b/include/net/devlink.h
@@ -1479,6 +1479,17 @@ void *devlink_priv(struct devlink *devlink);
 struct devlink *priv_to_devlink(void *priv);
 struct device *devlink_to_dev(const struct devlink *devlink);
 
+/* Devlink instance explicit locking */
+void devl_lock(struct devlink *devlink);
+void devl_unlock(struct devlink *devlink);
+void devl_assert_locked(struct devlink *devlink);
+bool devl_lock_is_held(struct devlink *devlink);
+
+int devl_port_register(struct devlink *devlink,
+		       struct devlink_port *devlink_port,
+		       unsigned int port_index);
+void devl_port_unregister(struct devlink_port *devlink_port);
+
 struct ib_device;
 
 struct net *devlink_net(const struct devlink *devlink);
diff --git a/net/core/devlink.c b/net/core/devlink.c
index fcd9f6d85cf1..c30da1fc023d 100644
--- a/net/core/devlink.c
+++ b/net/core/devlink.c
@@ -225,6 +225,37 @@ 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);
+
+bool devl_lock_is_held(struct devlink *devlink)
+{
+	/* We have to check this at runtime because struct devlink
+	 * is now private. Normally lock_is_held() should be eliminated
+	 * as dead code in the caller and we can depend on the linker error.
+	 */
+	if (!IS_ENABLED(CONFIG_LOCKDEP))
+		return WARN_ON_ONCE(true);
+
+	return lockdep_is_held(&devlink->lock);
+}
+EXPORT_SYMBOL_GPL(devl_lock_is_held);
+
+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 +9280,32 @@ 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 +9323,28 @@ 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 +9354,9 @@ 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);
 
-- 
2.34.1