Message ID | 20200608044111.ytOklZHdi%akpm@linux-foundation.org (mailing list archive) |
---|---|
State | New, archived |
Headers | show
Return-Path: <SRS0=PqO3=7V=kvack.org=owner-linux-mm@kernel.org> Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id A372D618 for <patchwork-linux-mm@patchwork.kernel.org>; Mon, 8 Jun 2020 04:41:15 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 708E320760 for <patchwork-linux-mm@patchwork.kernel.org>; Mon, 8 Jun 2020 04:41:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="bfmHsVTW" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 708E320760 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 84D9C6B0005; Mon, 8 Jun 2020 00:41:14 -0400 (EDT) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id 7D6616B0008; Mon, 8 Jun 2020 00:41:14 -0400 (EDT) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6ED3A6B0083; Mon, 8 Jun 2020 00:41:14 -0400 (EDT) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0087.hostedemail.com [216.40.44.87]) by kanga.kvack.org (Postfix) with ESMTP id 54BC36B0005 for <linux-mm@kvack.org>; Mon, 8 Jun 2020 00:41:14 -0400 (EDT) Received: from smtpin26.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 1C9081B646 for <linux-mm@kvack.org>; Mon, 8 Jun 2020 04:41:14 +0000 (UTC) X-FDA: 76904795268.26.sleep53_3e0523626db7 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin26.hostedemail.com (Postfix) with ESMTP id E7C9A1807946B for <linux-mm@kvack.org>; Mon, 8 Jun 2020 04:41:13 +0000 (UTC) X-Spam-Summary: 2,0,0,b1beb93bd44db3bf,d41d8cd98f00b204,akpm@linux-foundation.org,,RULES_HIT:41:69:152:355:379:800:960:967:973:988:989:1260:1263:1277:1311:1313:1314:1345:1359:1381:1431:1437:1513:1515:1516:1518:1521:1535:1543:1593:1594:1711:1730:1747:1777:1792:2198:2199:2393:2525:2553:2559:2566:2682:2685:2731:2859:2902:2933:2937:2939:2942:2945:2947:2951:2954:3022:3138:3139:3140:3141:3142:3354:3865:3866:3867:3868:3870:3871:3872:3874:3934:3936:3938:3941:3944:3947:3950:3953:3956:3959:4250:4321:4362:5007:6119:6261:6653:6737:7514:7576:7904:8599:9025:9545:10004:10226:10400:10913:11026:11658:11914:12043:12048:12050:12291:12296:12297:12438:12517:12519:12555:12679:12683:12783:12986:13161:13172:13180:13229:13846:14096:14097:14181:14721:14849:21080:21433:21451:21627:21939:30012:30054:30056:30064:30090,0,RBL:198.145.29.99:@linux-foundation.org:.lbl8.mailshell.net-64.100.201.201 62.2.0.100,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:fp,MSBL:0,DNSBL:neutra l,Custom X-HE-Tag: sleep53_3e0523626db7 X-Filterd-Recvd-Size: 5072 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf29.hostedemail.com (Postfix) with ESMTP for <linux-mm@kvack.org>; Mon, 8 Jun 2020 04:41:13 +0000 (UTC) Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 4CEFF20812; Mon, 8 Jun 2020 04:41:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591591272; bh=slw18Ar+EXfNW1zg5dKLZr1wO4FKOau9jsq6N1HPoyo=; h=Date:From:To:Subject:In-Reply-To:From; b=bfmHsVTWvmXy33/6z0c8CFoST5Bqw6RlAeZV4wkz674rvGVk3D9aERBKrUmm/+Tfl k+4xhrQDBwuOn1+GeZsKyAw5xMicZEsTdZVBOmRXGgAhPNp/E0OyvhPRsuXnBAvjgz 7dSS3B/u4Yar6x1dqCNiBjDSiQWpyNTkYtkTte9c= Date: Sun, 07 Jun 2020 21:41:11 -0700 From: Andrew Morton <akpm@linux-foundation.org> To: akpm@linux-foundation.org, corbet@lwn.net, david@fromorbit.com, jack@suse.cz, jasowang@redhat.com, jglisse@redhat.com, jhubbard@nvidia.com, jrdr.linux@gmail.com, linux-mm@kvack.org, mm-commits@vger.kernel.org, mst@redhat.com, torvalds@linux-foundation.org, vbabka@suse.cz Subject: [patch 21/54] docs: mm/gup: pin_user_pages.rst: add a "case 5" Message-ID: <20200608044111.ytOklZHdi%akpm@linux-foundation.org> In-Reply-To: <20200607212615.b050e41fac139a1e16fe00bd@linux-foundation.org> User-Agent: s-nail v14.8.16 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: E7C9A1807946B X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam04 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: <linux-mm.kvack.org> |
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[01/54] mm/page_idle.c: skip offline pages
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expand
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--- a/Documentation/core-api/pin_user_pages.rst~docs-mm-gup-pin_user_pagesrst-add-a-case-5 +++ a/Documentation/core-api/pin_user_pages.rst @@ -171,6 +171,24 @@ If only struct page data (as opposed to is tracking) is affected, then normal GUP calls are sufficient, and neither flag needs to be set. +CASE 5: Pinning in order to write to the data within the page +------------------------------------------------------------- +Even though neither DMA nor Direct IO is involved, just a simple case of "pin, +write to a page's data, unpin" can cause a problem. Case 5 may be considered a +superset of Case 1, plus Case 2, plus anything that invokes that pattern. In +other words, if the code is neither Case 1 nor Case 2, it may still require +FOLL_PIN, for patterns like this: + +Correct (uses FOLL_PIN calls): + pin_user_pages() + write to the data within the pages + unpin_user_pages() + +INCORRECT (uses FOLL_GET calls): + get_user_pages() + write to the data within the pages + put_page() + page_maybe_dma_pinned(): the whole point of pinning ===================================================