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=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 9CBA4C433ED for ; Mon, 10 May 2021 05:08:38 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id F12AF61424 for ; Mon, 10 May 2021 05:08:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F12AF61424 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 59EE46B0070; Mon, 10 May 2021 01:08:37 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 54F796B0071; Mon, 10 May 2021 01:08:37 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4169F6B0072; Mon, 10 May 2021 01:08:37 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0069.hostedemail.com [216.40.44.69]) by kanga.kvack.org (Postfix) with ESMTP id 266B96B0070 for ; Mon, 10 May 2021 01:08:37 -0400 (EDT) Received: from smtpin11.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id D20458138 for ; Mon, 10 May 2021 05:08:36 +0000 (UTC) X-FDA: 78124141032.11.DE7A68A Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf12.hostedemail.com (Postfix) with ESMTP id 01FE9138 for ; Mon, 10 May 2021 05:08:20 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 494FF61432; Mon, 10 May 2021 05:08:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1620623315; bh=4J6MTW8s/x4YXb+wRdoYSsxhvgYN6Y+/LU8YxgkjqtE=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=b4MVlq5fdsrsun5cQiFvyh4aV6wCWngXpNB4TL7x8pN+jqf0CcP0ymD14Kqjnf968 d8xUyvzIf8fFy1bdADyvLa4IWpD9znEfhjnDh6DIIlwNKtnv6p9zJ3p/HgO4auc/le luwFE2Ksc5A+PZh7z+D+9g5Q36q+71sB51IiIQGQ= Date: Sun, 9 May 2021 22:08:34 -0700 From: Andrew Morton To: Gonzalo Matias Juarez Tello Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/mmap.c: logic of find_vma_intersection repeated in __do_munmap Message-Id: <20210509220834.d8b46dabea050d162df8cdf7@linux-foundation.org> In-Reply-To: <20210409162129.18313-1-gmjuareztello@gmail.com> References: <20210409162129.18313-1-gmjuareztello@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 Authentication-Results: imf12.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=b4MVlq5f; dmarc=none; spf=pass (imf12.hostedemail.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 01FE9138 X-Stat-Signature: pdyobq3ngiekqhm1dit1b1f4dx9uy5ns Received-SPF: none (linux-foundation.org>: No applicable sender policy available) receiver=imf12; identity=mailfrom; envelope-from=""; helo=mail.kernel.org; client-ip=198.145.29.99 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1620623300-567136 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000012, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, 9 Apr 2021 13:21:26 -0300 Gonzalo Matias Juarez Tello wrote: > Logic of find_vma_intersection() (which is an inline fc) is > repeated in __do_munmap(). > Besides, prev is assigned a value before checking vma->vm_start >= end > which might end up on a return statement making that assignment useless. > > Calling find_vma_intersection() checks that condition and returns NULL if > no vma is found, hence only the !vma check is needed in __do_munmap(). > > ... > > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -2822,16 +2822,11 @@ int __do_munmap(struct mm_struct *mm, unsigned long start, size_t len, > */ > arch_unmap(mm, start, end); > > - /* Find the first overlapping VMA */ > - vma = find_vma(mm, start); > + /* Find the first overlapping VMA where start < vma->vm_end */ > + vma = find_vma_intersection(mm, start, end); > if (!vma) > return 0; > prev = vma->vm_prev; > - /* we have start < vma->vm_end */ > - > - /* if it doesn't overlap, we have nothing.. */ > - if (vma->vm_start >= end) > - return 0; > > /* > * If we need to split any vma, do it now to save pain later. Looks good to me, thanks.