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=-5.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 5A6DDC35240 for ; Fri, 31 Jan 2020 03:19:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3056E214D8 for ; Fri, 31 Jan 2020 03:19:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="DyboAuvv" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727931AbgAaDTe (ORCPT ); Thu, 30 Jan 2020 22:19:34 -0500 Received: from hqnvemgate24.nvidia.com ([216.228.121.143]:6618 "EHLO hqnvemgate24.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727831AbgAaDTd (ORCPT ); Thu, 30 Jan 2020 22:19:33 -0500 Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate24.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Thu, 30 Jan 2020 19:18:38 -0800 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Thu, 30 Jan 2020 19:19:31 -0800 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Thu, 30 Jan 2020 19:19:31 -0800 Received: from [10.110.48.28] (10.124.1.5) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Fri, 31 Jan 2020 03:19:31 +0000 Subject: Re: [PATCH v2 4/8] mm/gup: track FOLL_PIN pages To: "Kirill A. Shutemov" CC: Andrew Morton , Al Viro , Christoph Hellwig , Dan Williams , Dave Chinner , Ira Weiny , Jan Kara , Jason Gunthorpe , Jonathan Corbet , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , Michal Hocko , Mike Kravetz , Shuah Khan , Vlastimil Babka , , , , , , LKML , "Kirill A . Shutemov" References: <20200129032417.3085670-1-jhubbard@nvidia.com> <20200129032417.3085670-5-jhubbard@nvidia.com> <20200129135153.knie7ptvsxcgube6@box> <0be743df-e9af-6da9-c593-9e25ab194acf@nvidia.com> <20200130113126.5ftq4gd5k7o7tipj@box> From: John Hubbard X-Nvconfidentiality: public Message-ID: <1037b514-30e7-c128-38c1-9c98488be337@nvidia.com> Date: Thu, 30 Jan 2020 19:19:30 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.2 MIME-Version: 1.0 In-Reply-To: <20200130113126.5ftq4gd5k7o7tipj@box> X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL105.nvidia.com (172.20.187.12) To HQMAIL107.nvidia.com (172.20.187.13) Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1580440719; bh=9n3GVRH7rJT8PUMEqe1BMiXjCWR5u2839yBFWtobbC8=; h=X-PGP-Universal:Subject:To:CC:References:From:X-Nvconfidentiality: Message-ID:Date:User-Agent:MIME-Version:In-Reply-To: X-Originating-IP:X-ClientProxiedBy:Content-Type:Content-Language: Content-Transfer-Encoding; b=DyboAuvvbnzLHMEIag1fx4ad2eQQcY8Jsk0DPogA1Xd5f6sbkghXewV7YQM2/iusj B4T31MmPGDxl8HYQEgTzwTjtC7aXYSsBqhReBchu4rQ3x2Tg9oKG30YhyaXyxX1zNJ mQXxsLzBUV1RQ6IAEVYKzDedk9H7zC8YcXryZqWQmOBJN6TCbJzzlnCBXNPqKb3tHz gb7xzJ5ZNfj8tLSN3LebvHbUjchA/wB6wHtGy1YqbyoHTg/Hy4dFqQ3WNC6LGHaugE phaII7jurRZGdzUGIVeJaTPP7ZEu9NHyZD6tjX5kAaACjvJbQ8wCOySgAH5vXtg5+O 50R/K9o+IjDKA== Sender: linux-kselftest-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org On 1/30/20 3:31 AM, Kirill A. Shutemov wrote: ... >>>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >>>> index 0a55dec68925..b1079aaa6f24 100644 >>>> --- a/mm/huge_memory.c >>>> +++ b/mm/huge_memory.c >>>> @@ -958,6 +958,11 @@ struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr, >>>> */ >>>> WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set"); >>>> + /* FOLL_GET and FOLL_PIN are mutually exclusive. */ >>>> + if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) == >>>> + (FOLL_PIN | FOLL_GET))) >>> >>> Too many parentheses. >> >> >> OK, I'll remove at least one. :) > > I see two. ah, correction: actually, the original statement has exactly the right number of parentheses. The relevant C precedence order is: == & | ...which means that both "&" and "|" operations need parentheses protection from the higher precedence "==" operation. (There are other places in the kernel that have this exact pattern, too, with the same pattern of parentheses that I'm using, of course.) thanks, -- John Hubbard NVIDIA