btrfs_lookup_inode
ret = btrfs_lookup_inode(trans, root, path, &key, mod);
int btrfs_lookup_inode(struct btrfs_trans_handle *trans,
ret = btrfs_lookup_inode(NULL, root, path, &location, 0);
ret = btrfs_lookup_inode(trans, inode->root, path, &key, 1);
ret = btrfs_lookup_inode(trans, root, wc->subvol_path, &log_key, 0);