From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AD697C433E0 for ; Tue, 4 Aug 2020 03:25:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A9FF42068F for ; Tue, 4 Aug 2020 03:25:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1596511519; bh=OkGwV19lvozFPP7dvqytHQBH60u/k0mvdZOQB1UkLE8=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=Kr6oJWpAB4wW+UI9EmD9St1uKb4r4+EjRZNEq9yyrhyejuPg2axnVj8d6EPmh0Bqq WC/bjoFSId1kqRs81By/pUkGXVzhNe+N6Yq0Ex1Wqy4PrLPOpYP3+qhVY0xtVo5Y55 /OLhoZxMRxc3/6I9VUgEOLX5zDL+YYhVJkz4OGRE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730194AbgHDDZS (ORCPT ); Mon, 3 Aug 2020 23:25:18 -0400 Received: from mail.kernel.org ([198.145.29.99]:41190 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725840AbgHDDZR (ORCPT ); Mon, 3 Aug 2020 23:25:17 -0400 Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 889392068F; Tue, 4 Aug 2020 03:25:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1596511517; bh=OkGwV19lvozFPP7dvqytHQBH60u/k0mvdZOQB1UkLE8=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Y/Ch27bn+/Ew9z341puf5vUzKvpE8kaoo2Ovhp5JSZ6/z9CIlRnJhpgV+6TDqBF5X wWxgClB9pQHnM1gHsE+2UEk8OF0MTn8/CkP6Dv2I4+D9LdOocSScHMXUF1lUWmHluT PUH6/jfafCch42+cqqBRgWgnlR4aJm/ng1E9Scpg= Date: Mon, 3 Aug 2020 20:25:16 -0700 From: Andrew Morton To: Wenchao Hao Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm, mempolicy: Check parameters first in kernel_get_mempolicy Message-Id: <20200803202516.5d6c1c770137cb35a288f514@linux-foundation.org> In-Reply-To: <20200801090825.5597-1-haowenchao22@gmail.com> References: <20200801090825.5597-1-haowenchao22@gmail.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 1 Aug 2020 17:08:26 +0800 Wenchao Hao wrote: > Previous implement called untagged_addr before error check, while > if the error check failed and return EINVAL, the untagged_addr is > just useless work. > > ... > > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -1632,11 +1632,11 @@ static int kernel_get_mempolicy(int __user *policy, > int uninitialized_var(pval); > nodemask_t nodes; > > - addr = untagged_addr(addr); > - > if (nmask != NULL && maxnode < nr_node_ids) > return -EINVAL; > > + addr = untagged_addr(addr); > + > err = do_get_mempolicy(&pval, &nodes, addr, flags); > > if (err) Well, the compiler will surely avoid that useless work. But the code is better this way.