zonefs: Fix race between modprobe and mount

There is a race between modprobe and mount as below:

 modprobe zonefs                | mount -t zonefs
--------------------------------|-------------------------
 zonefs_init                    |
  register_filesystem       [1] |
                                | zonefs_fill_super    [2]
  zonefs_sysfs_init         [3] |

1. register zonefs suceess, then
2. user can mount the zonefs
3. if sysfs initialize failed, the module initialize failed.

Then the mount process maybe some error happened since the module
initialize failed.

Let's register zonefs after all dependency resource ready. And
reorder the dependency resource release in module exit.

Fixes: 9277a6d4 ("zonefs: Export open zone resource information through sysfs")
Signed-off-by: Zhang Xiaoxu <zhangxiaoxu5@huawei.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>

fs/zonefs/super.c

@@ -1922,18 +1922,18 @@ static int __init zonefs_init(void)
 	if (ret)
 		return ret;
 
-	ret = register_filesystem(&zonefs_type);
+	ret = zonefs_sysfs_init();
 	if (ret)
 		goto destroy_inodecache;
 
-	ret = zonefs_sysfs_init();
+	ret = register_filesystem(&zonefs_type);
 	if (ret)
-		goto unregister_fs;
+		goto sysfs_exit;
 
 	return 0;
 
-unregister_fs:
-	unregister_filesystem(&zonefs_type);
+sysfs_exit:
+	zonefs_sysfs_exit();
 destroy_inodecache:
 	zonefs_destroy_inodecache();
 
@@ -1942,9 +1942,9 @@ static int __init zonefs_init(void)
 
 static void __exit zonefs_exit(void)
 {
+	unregister_filesystem(&zonefs_type);
 	zonefs_sysfs_exit();
 	zonefs_destroy_inodecache();
-	unregister_filesystem(&zonefs_type);
 }
 
 MODULE_AUTHOR("Damien Le Moal");