rem: err = EINVAL;
add: err = FS_EINVAL;
context: sys_mkdir(bool kernel, int fd, const char *path, int perms){    int             err;    char            filename[FILE_NAME_LENGTH];    vnode           *dvn;    op_mkdir        *op;    err = get_dir_fd(kernel, fd, path, filename, &dvn);    if (err)        goto error1;    op = dvn->ns->fs->ops.mkdir;    if (!op) {        err = EINVAL;        goto error2;    }    err = (*op)(dvn->ns->data, dvn->data, filename, perms);    if (err)        goto error2;    dec_vnode(dvn, FALSE);    return 0;error2:    dec_vnode(dvn, FALSE);error1:    return err;}