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=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 39DE5C388F7 for ; Sat, 7 Nov 2020 19:17:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id ED4FB207C3 for ; Sat, 7 Nov 2020 19:17:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="nedmNtDm" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728656AbgKGTRy (ORCPT ); Sat, 7 Nov 2020 14:17:54 -0500 Received: from hqnvemgate24.nvidia.com ([216.228.121.143]:5730 "EHLO hqnvemgate24.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725836AbgKGTRx (ORCPT ); Sat, 7 Nov 2020 14:17:53 -0500 Received: from hqmail.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate24.nvidia.com (using TLS: TLSv1.2, AES256-SHA) id ; Sat, 07 Nov 2020 11:17:57 -0800 Received: from [10.2.62.222] (172.20.13.39) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Sat, 7 Nov 2020 19:17:52 +0000 Subject: Re: [PATCH 1/2] tomoyo: Convert get_user_pages*() to pin_user_pages*() From: John Hubbard To: Souptick Joarder , , , , CC: , , Jan Kara , Matthew Wilcox References: <1604737451-19082-1-git-send-email-jrdr.linux@gmail.com> Message-ID: Date: Sat, 7 Nov 2020 11:17:52 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [172.20.13.39] X-ClientProxiedBy: HQMAIL107.nvidia.com (172.20.187.13) To HQMAIL107.nvidia.com (172.20.187.13) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1604776677; bh=yfhdGpRJZc3CvodI5i1IHo+KRBmzHgvXgzVSoUCFcYw=; h=Subject:From:To:CC:References:Message-ID:Date:User-Agent: MIME-Version:In-Reply-To:Content-Type:Content-Language: Content-Transfer-Encoding:X-Originating-IP:X-ClientProxiedBy; b=nedmNtDmoYJfgU992ShmtCC57esM3aLP4lFDsq2VsnRlkgg0vOHucUb25U9gXt0Ui bb46/ufveki0qfrIbDUrdScf5MsqEn/41KZDkL8VMlaTQYixjrZvxgt1S2YBf3lLvh rPqMwfsyGVuVIK5pTa1yry0dJhEqS4MtlTMG2pLS2ZvMvSOkqlMZhSkP0SdnA0jAe6 P2w7IfbrVikCQpNZmVXjazWbJnkzn9y9wrIhJ6EPe+PIa+Rec/wtXsQRKp0Vfre2Kr hbZsXxzeQETQO4DlWHK1dqVwxwM1l7RGyJ/wtLkBRkz1twUZCzdfsIOZOPCrU8A4GB jk38FeRVwJ65g== Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/7/20 1:04 AM, John Hubbard wrote: > On 11/7/20 12:24 AM, Souptick Joarder wrote: >> In 2019, we introduced pin_user_pages*() and now we are converting >> get_user_pages*() to the new API as appropriate. [1] & [2] could >> be referred for more information. This is case 5 as per document [1]. > > It turns out that Case 5 can be implemented via a better pattern, as long > as we're just dealing with a page at a time, briefly: > > lock_page() > write to page's data > unlock_page() > > ...which neatly synchronizes with writeback and other fs activities. Ahem, I left out a key step: set_page_dirty()! lock_page() write to page's data set_page_dirty() unlock_page() thanks, -- John Hubbard NVIDIA