rem: err = ENOTDIR;
add: err = FS_ENOTDIR;
context: rootfs_opendir(void *_ns, void *_node, void **cookie){    nspace      *ns;    vnode       *node;    int         err;    dirpos      *pos;    ns = (nspace *) _ns;    node = (vnode *) _node;    if (!MY_S_ISDIR(node->mode)) {        err = ENOTDIR;        goto error1;    }    pos = (dirpos *) malloc(sizeof(dirpos));    if (!pos) {        err = ENOMEM;        goto error1;    }    if (new_lock(&pos->lock, "rootdirlock") < 0) {        err = EINVAL;        goto error2;    }    pos->pos = 0;    pos->name[0] = '\0';    *cookie = pos;    return 0;error2:    free(pos);error1:    return err;}