rem: err = EBADF;
add: err = FS_EBADF;
context: sys_remove_attr(bool kernel, int fd, const char *name){    ofile       *f;    int         err;    vnode       *vn;    f = get_fd(kernel, fd, FD_FILE);    if (!f) {        err = EBADF;        goto error1;    }    vn = f->vn;    err = (*vn->ns->fs->ops.remove_attr)(vn->ns->data, vn->data, name);    if (err)        goto error2;    put_fd(f);    return 0;error2:    put_fd(f);  error1:    return err;}