IB/cm: Fix infiniband_cm class kobject ref counting

Commit 9af57b7a ("IB/cm: Add basic performance counters") introduced a
bug in how the reference count for cm_class.subsys.kobj was handled:
the path that released a device did a kobject_put() on that kobject, but
there was no kobject_get() in the path the handles adding a device.  So
the reference count ended up too low, which leads to bad things.  Fix up
and simplify the reference counting to avoid this.

(Actually, I introduced the bug when fixing the patch up to match some
of Greg's kobject changes, but who's counting)
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/core/cm.c

@@ -3612,18 +3612,12 @@ struct class cm_class = {
 };
 EXPORT_SYMBOL(cm_class);
 
-static void cm_remove_fs_obj(struct kobject *obj)
-{
-	kobject_put(obj->parent);
-	kobject_put(obj);
-}
-
 static int cm_create_port_fs(struct cm_port *port)
 {
 	int i, ret;
 
 	ret = kobject_init_and_add(&port->port_obj, &cm_port_obj_type,
-				   kobject_get(&port->cm_dev->dev_obj),
+				   &port->cm_dev->dev_obj,
 				   "%d", port->port_num);
 	if (ret) {
 		kfree(port);
@@ -3633,7 +3627,7 @@ static int cm_create_port_fs(struct cm_port *port)
 	for (i = 0; i < CM_COUNTER_GROUPS; i++) {
 		ret = kobject_init_and_add(&port->counter_group[i].obj,
 					   &cm_counter_obj_type,
-					   kobject_get(&port->port_obj),
+					   &port->port_obj,
 					   "%s", counter_group_names[i]);
 		if (ret)
 			goto error;
@@ -3643,8 +3637,8 @@ static int cm_create_port_fs(struct cm_port *port)
 
 error:
 	while (i--)
-		cm_remove_fs_obj(&port->counter_group[i].obj);
-	cm_remove_fs_obj(&port->port_obj);
+		kobject_put(&port->counter_group[i].obj);
+	kobject_put(&port->port_obj);
 	return ret;
 
 }
@@ -3654,9 +3648,9 @@ static void cm_remove_port_fs(struct cm_port *port)
 	int i;
 
 	for (i = 0; i < CM_COUNTER_GROUPS; i++)
-		cm_remove_fs_obj(&port->counter_group[i].obj);
+		kobject_put(&port->counter_group[i].obj);
 
-	cm_remove_fs_obj(&port->port_obj);
+	kobject_put(&port->port_obj);
 }
 
 static void cm_add_one(struct ib_device *device)
@@ -3740,7 +3734,7 @@ error1:
 		ib_unregister_mad_agent(port->mad_agent);
 		cm_remove_port_fs(port);
 	}
-	cm_remove_fs_obj(&cm_dev->dev_obj);
+	kobject_put(&cm_dev->dev_obj);
 }
 
 static void cm_remove_one(struct ib_device *device)
@@ -3767,7 +3761,7 @@ static void cm_remove_one(struct ib_device *device)
 		ib_unregister_mad_agent(port->mad_agent);
 		cm_remove_port_fs(port);
 	}
-	cm_remove_fs_obj(&cm_dev->dev_obj);
+	kobject_put(&cm_dev->dev_obj);
 }
 
 static int __init ib_cm_init(void)