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 73F5EC433DF for ; Tue, 4 Aug 2020 03:25:20 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 60E6D206DA for ; Tue, 4 Aug 2020 03:25:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="Y/Ch27bn" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 60E6D206DA Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 8B8CC8D0122; Mon, 3 Aug 2020 23:25:19 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 869F98D0081; Mon, 3 Aug 2020 23:25:19 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 77F6C8D0122; Mon, 3 Aug 2020 23:25:19 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0030.hostedemail.com [216.40.44.30]) by kanga.kvack.org (Postfix) with ESMTP id 633778D0081 for ; Mon, 3 Aug 2020 23:25:19 -0400 (EDT) Received: from smtpin07.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 0AA883624 for ; Tue, 4 Aug 2020 03:25:19 +0000 (UTC) X-FDA: 77111445558.07.talk22_31098eb26fa3 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin07.hostedemail.com (Postfix) with ESMTP id D83F81803F9A3 for ; Tue, 4 Aug 2020 03:25:18 +0000 (UTC) X-HE-Tag: talk22_31098eb26fa3 X-Filterd-Recvd-Size: 2262 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf39.hostedemail.com (Postfix) with ESMTP for ; Tue, 4 Aug 2020 03:25:18 +0000 (UTC) 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 X-Rspamd-Queue-Id: D83F81803F9A3 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam01 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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.