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=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, 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 A267AC3F2C6 for ; Sat, 29 Feb 2020 20:07:05 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 60BF824688 for ; Sat, 29 Feb 2020 20:07:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="IEDvST0Q" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 60BF824688 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=nvidia.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id DB3876B0005; Sat, 29 Feb 2020 15:07:04 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id D3C796B0006; Sat, 29 Feb 2020 15:07:04 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C047B6B0007; Sat, 29 Feb 2020 15:07:04 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0187.hostedemail.com [216.40.44.187]) by kanga.kvack.org (Postfix) with ESMTP id A42EC6B0005 for ; Sat, 29 Feb 2020 15:07:04 -0500 (EST) Received: from smtpin04.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 69C6652D1 for ; Sat, 29 Feb 2020 20:07:04 +0000 (UTC) X-FDA: 76544248368.04.air15_77e2954386600 X-HE-Tag: air15_77e2954386600 X-Filterd-Recvd-Size: 4030 Received: from hqnvemgate26.nvidia.com (hqnvemgate26.nvidia.com [216.228.121.65]) by imf13.hostedemail.com (Postfix) with ESMTP for ; Sat, 29 Feb 2020 20:07:03 +0000 (UTC) Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate26.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Sat, 29 Feb 2020 12:06:48 -0800 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Sat, 29 Feb 2020 12:07:02 -0800 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Sat, 29 Feb 2020 12:07:02 -0800 Received: from ngvpn01-175-70.dyn.scz.us.nvidia.com (10.124.1.5) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Sat, 29 Feb 2020 20:07:02 +0000 Subject: Re: [RFC v1 2/2] mm/gup/writeback: add callbacks for inaccessible pages To: Claudio Imbrenda CC: Christian Borntraeger , , , , , , , , , , Will Deacon References: <20200228154322.329228-1-imbrenda@linux.ibm.com> <20200228154322.329228-4-imbrenda@linux.ibm.com> <2e3bf1a2-b672-68e0-97b6-42f08133e077@de.ibm.com> <20200229114919.1abcacc4@p-imbrenda> X-Nvconfidentiality: public From: John Hubbard Message-ID: Date: Sat, 29 Feb 2020 12:07:01 -0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200229114919.1abcacc4@p-imbrenda> X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL101.nvidia.com (172.20.187.10) To HQMAIL107.nvidia.com (172.20.187.13) Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1583006808; bh=Wmoswp92q0ncm0Ak5aD4Ct5WPC9Xr+W7Or+k/XZL7Is=; h=X-PGP-Universal:Subject:To:CC:References:X-Nvconfidentiality:From: Message-ID:Date:User-Agent:MIME-Version:In-Reply-To: X-Originating-IP:X-ClientProxiedBy:Content-Type:Content-Language: Content-Transfer-Encoding; b=IEDvST0Qu3TviUS7V12sJ4TOu7edmLi+/7WRbx9igEIGIOaNGTA3kjoWTIFKQmsyD gLt++MWZMnlo7FVlceSiyCTdzqR51twboBlnGmtaOAilyPW8I3RA4sX2CwU6biC1c+ p2QswktYWRuYLOdte9iX3FCaFfoEZASsJ5uCVBaCBes73UZT6CeGTexPBB8uZiDQz7 cXba/nhb9u7YuXj5uerkShAuVS2wlOPUDPK2DYAWdDO+vf6Ht0EYKeU1m3vbskR2JI v+7IdMQ4lSHdbUyj1TrA2xm2/RlKXH/uj6RuEehCR8klC/bZsUabtZQyGEsWGHzk1A zesSNT3fxEn7A== 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 2/29/20 2:49 AM, Claudio Imbrenda wrote: >> ... >>>> @@ -458,7 +457,6 @@ static struct page *follow_page_pte(struct >>>> vm_area_struct *vma, } >>>> >>>> if (flags & FOLL_SPLIT && PageTransCompound(page)) { >>>> - int ret; >>>> get_page(page); >>>> pte_unmap_unlock(ptep, ptl); >>>> lock_page(page); >>>> @@ -475,6 +473,14 @@ static struct page *follow_page_pte(struct >>>> vm_area_struct *vma, page = ERR_PTR(-ENOMEM); >>>> goto out; >>>> } >>>> + if (flags & FOLL_PIN) { >> >> >> What about FOLL_GET? Unless your calling code has some sort of >> BUG_ON(flags & FOLL_GET), I'm not sure it's a good idea to leave that >> case unhandled. > > if I understood the semantics of FOLL_PIN correctly, then we don't need > to make the page accessible for FOLL_GET. FOLL_PIN indicates intent to > access the content of the page, whereas FOLL_GET is only for the struct > page. > > if we are not touching the content of the page, there is no need to > make it accessible > OK, I hope I'm not overlooking anything, but that sounds correct to me. thanks, -- John Hubbard NVIDIA