struct btrfs_root *root,
                               struct btrfs_root *parent_root)
 {
+       struct super_block *sb = root->fs_info->sb;
        struct btrfs_key key;
        struct inode *parent_inode, *child_inode;
        int ret;
        key.type = BTRFS_INODE_ITEM_KEY;
        key.offset = 0;
 
-       parent_inode = btrfs_iget(parent_root->fs_info->sb, &key,
-                                 parent_root, NULL);
+       parent_inode = btrfs_iget(sb, &key, parent_root, NULL);
        if (IS_ERR(parent_inode))
                return PTR_ERR(parent_inode);
 
-       child_inode = btrfs_iget(root->fs_info->sb, &key, root, NULL);
+       child_inode = btrfs_iget(sb, &key, root, NULL);
        if (IS_ERR(child_inode)) {
                iput(parent_inode);
                return PTR_ERR(child_inode);