Btrfs: insert orphan roots into fs radix tree

Now we don't drop all the deleted snapshots/subvolumes before the space
balance. It means we have to relocate the space which is held by the dead
snapshots/subvolumes. So we must into them into fs radix tree, or we would
forget to commit the change of them when doing transaction commit, and it
would corrupt the metadata.
Signed-off-by: NMiao Xie <miaox@cn.fujitsu.com>
Signed-off-by: NJosef Bacik <jbacik@fusionio.com>
Signed-off-by: NChris Mason <chris.mason@fusionio.com>

fs/btrfs/root-tree.c

@@ -299,11 +299,6 @@ int btrfs_find_orphan_roots(struct btrfs_root *tree_root)
 			continue;
 		}
 
-		if (btrfs_root_refs(&root->root_item) == 0) {
-			btrfs_add_dead_root(root);
-			continue;
-		}
-
 		err = btrfs_init_fs_root(root);
 		if (err) {
 			btrfs_free_fs_root(root);
@@ -318,6 +313,9 @@ int btrfs_find_orphan_roots(struct btrfs_root *tree_root)
 			btrfs_free_fs_root(root);
 			break;
 		}
+
+		if (btrfs_root_refs(&root->root_item) == 0)
+			btrfs_add_dead_root(root);
 	}
 
 	btrfs_free_path(path);