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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 69C0CC433F5 for ; Wed, 6 Apr 2022 13:59:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234202AbiDFOBV (ORCPT ); Wed, 6 Apr 2022 10:01:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48062 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234016AbiDFOBI (ORCPT ); Wed, 6 Apr 2022 10:01:08 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BB1532414EE for ; Wed, 6 Apr 2022 02:17:53 -0700 (PDT) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.53]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4KYJlq3rpHzgYSy; Wed, 6 Apr 2022 17:16:07 +0800 (CST) Received: from [10.174.177.76] (10.174.177.76) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Wed, 6 Apr 2022 17:17:51 +0800 Subject: Re: [PATCH] mm/mlock: remove unneeded start >= vma->vm_end check From: Miaohe Lin To: Matthew Wilcox , Andrew Morton CC: , , References: <20220314153223.53753-1-linmiaohe@huawei.com> Message-ID: <58fcd181-cadb-1e61-fc18-9994b93bb1bc@huawei.com> Date: Wed, 6 Apr 2022 17:17:51 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/3/15 20:30, Miaohe Lin wrote: > On 2022/3/15 0:17, Matthew Wilcox wrote: >> On Mon, Mar 14, 2022 at 11:32:23PM +0800, Miaohe Lin wrote: >>> If find_vma returns a vma, it must satisfies that start < vma->vm_end. >>> Since vma list is sorted in the ascending order, so we will never see >>> start >= vma->vm_end here. Remove this unneeded check. >> >> faulty logic; vm_start + len might wrap. What do you mean is vm_start + len might wrap, so vm_end might be < vm_start ? If so, this could not happen as get_unmapped_area guarantees this. > > Many thanks for comment. I agree with you about "vm_start + len" might wrap. > But what I mean here is that we will never see "start" >= vma->vm_end here > as find_vma guarantees this. And I leave the "start + len <= vma->vm_start" > check untouched. So my cleanup should be right. Or am I miss something? So I think this "start >= vma->vm_end" check is unneeded and we can remove it. Or am I miss something? Many thanks! > > Thanks. > >> >> . >> >