btrfs: set the total_devices in device_list_add()

There is no other parent for device_list_add() except for
btrfs_scan_one_device(), which would set btrfs_fs_devices::total_devices
if device_list_add is successful and this can be done with in
device_list_add() itself.
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/volumes.c

@@ -841,6 +841,8 @@ static noinline int device_list_add(const char *path,
 	if (!fs_devices->opened)
 		device->generation = found_transid;
 
+	fs_devices->total_devices = btrfs_super_num_devices(disk_super);
+
 	*fs_devices_ret = fs_devices;
 
 	return 0;
@@ -1182,7 +1184,6 @@ int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
 	struct page *page;
 	int ret;
 	u64 devid;
-	u64 total_devices;
 	u64 bytenr;
 
 	/*
@@ -1207,11 +1208,8 @@ int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
 	}
 
 	devid = btrfs_stack_device_id(&disk_super->dev_item);
-	total_devices = btrfs_super_num_devices(disk_super);
 
 	ret = device_list_add(path, disk_super, devid, fs_devices_ret);
-	if (!ret && fs_devices_ret)
-		(*fs_devices_ret)->total_devices = total_devices;
 
 	btrfs_release_disk_super(page);