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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 97790C433FE for ; Fri, 22 Apr 2022 05:56:52 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 109C56B0072; Fri, 22 Apr 2022 01:56:52 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0BA106B0073; Fri, 22 Apr 2022 01:56:52 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E9DFA6B0074; Fri, 22 Apr 2022 01:56:51 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.a.hostedemail.com [64.99.140.24]) by kanga.kvack.org (Postfix) with ESMTP id DA7E86B0072 for ; Fri, 22 Apr 2022 01:56:51 -0400 (EDT) Received: from smtpin27.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay11.hostedemail.com (Postfix) with ESMTP id 9AD05808E2 for ; Fri, 22 Apr 2022 05:56:51 +0000 (UTC) X-FDA: 79383456222.27.FA4EBA4 Received: from NAM11-BN8-obe.outbound.protection.outlook.com (mail-bn8nam11on2078.outbound.protection.outlook.com [40.107.236.78]) by imf04.hostedemail.com (Postfix) with ESMTP id DC4924001A for ; Fri, 22 Apr 2022 05:56:47 +0000 (UTC) ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=YL+1MVBao09sISNnlJENAIM+BosBamZqmvJrA5sETc9u/QTj3s2EfPxQM+aiX8gZI5GALTHlQ9twGJZqOuanyU0G4AucIg/fsx0bT02V5JiZwOri3aCZLT2AcBtJC7+jIi/PxsWb3DPdahzqOjxCs1lyEu0qtXoX3Z9DFvJyXt08/Q33S2rd4nmHSIkR9e9KlwO2il7YznhYEXaN6FpEZf0SWLwgxdZOIhX7NqyHxExLFcbevHHrGu/oN4ySN8CdKtKTQOn+xaEMJAJtPDk4880Ekm3Gp1B3nOezo+768tZ5UPSqB6FSxpaKD8HZovLr/Op1TJ07JUc5Xkih+om3Eg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=rpZcvwAuknmWY6JauQ6sNBC0ZbTS5OQb+1lSzSQg9Bs=; b=R/mZtUMVboRKUhR2Ybsz+ImmNKP2Pf0XTe8Dtn+FsPV3pHvMFUvJrfPI09bLqqD4kD1RgcGOnAyjW/2OocNFn+ugwzwooMYpXM2e0udnbQ2qDhg8YREtI9rUr45n8taNS+D+NSo5HCVj/i8qhQr2NomPOsX6YS/bclSQqbZ+0OXTaWZuO73akEalIOPDU13fsMnI1Gfy1m+AbD4T7bfwyHcfBPuqOGf/D9oRpUDYFm1fX7pXioYqyY7ePuHi2pwUsYzoTPFKTrbnwL24CXYhLc5VKMQOMjc6IE+3b3/ek4HUNt6eTJSaxgwfCDbg3/y1dPuPCuUF2OiJ/4X8jLp9Vg== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass (sender ip is 12.22.5.238) smtp.rcpttodomain=kvack.org smtp.mailfrom=nvidia.com; dmarc=pass (p=reject sp=reject pct=100) action=none header.from=nvidia.com; dkim=none (message not signed); arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=Nvidia.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=rpZcvwAuknmWY6JauQ6sNBC0ZbTS5OQb+1lSzSQg9Bs=; b=QF0WU3XQ6vuk2U7yKieyHAk+iQLTZYjV0+8b/cvLjIG+EIYwvySh2IQ5gWAgSutho1BoOZcOcnbgUWEbufPKPIj6zH72bUsS9SAM2vIzKEvdey5Ahug8c/8DjDBfddyUsG9gfOHcd6wZsdRLmqJ8X/AO3Pqd8eBo5BFSSuR+6n5a5+zYP/mjoMUaCCphUG3G2FiIasPl8XWe3jFHzjIjSAEF0hkM2RD7SCR+yeD8lsrO8W9PGkOC5jG7YxFXE30/cPgW8lVljyyqyfNbApklu1ft71kMpyWYPYASFpfYi6YvxApiJjcO+cxAiPaL2dHPK0lOpSz6jqgSRvEyZu2T1w== Received: from DM6PR03CA0066.namprd03.prod.outlook.com (2603:10b6:5:100::43) by DM4PR12MB6301.namprd12.prod.outlook.com (2603:10b6:8:a5::21) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.5164.20; Fri, 22 Apr 2022 05:56:47 +0000 Received: from DM6NAM11FT004.eop-nam11.prod.protection.outlook.com (2603:10b6:5:100:cafe::64) by DM6PR03CA0066.outlook.office365.com (2603:10b6:5:100::43) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.5186.15 via Frontend Transport; Fri, 22 Apr 2022 05:56:47 +0000 X-MS-Exchange-Authentication-Results: spf=pass (sender IP is 12.22.5.238) smtp.mailfrom=nvidia.com; dkim=none (message not signed) header.d=none;dmarc=pass action=none header.from=nvidia.com; Received-SPF: Pass (protection.outlook.com: domain of nvidia.com designates 12.22.5.238 as permitted sender) receiver=protection.outlook.com; client-ip=12.22.5.238; helo=mail.nvidia.com; Received: from mail.nvidia.com (12.22.5.238) by DM6NAM11FT004.mail.protection.outlook.com (10.13.172.217) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id 15.20.5186.14 via Frontend Transport; Fri, 22 Apr 2022 05:56:46 +0000 Received: from rnnvmail201.nvidia.com (10.129.68.8) by DRHQMAIL105.nvidia.com (10.27.9.14) with Microsoft SMTP Server (TLS) id 15.0.1497.32; Fri, 22 Apr 2022 05:56:46 +0000 Received: from [10.110.48.28] (10.126.230.35) by rnnvmail201.nvidia.com (10.129.68.8) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.986.22; Thu, 21 Apr 2022 22:56:45 -0700 Message-ID: <398cae59-b4c7-19d5-af67-6f36546fce01@nvidia.com> Date: Thu, 21 Apr 2022 22:56:59 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.8.1 Subject: Re: [PATCH v2] mm/gup: fix comments to pin_user_pages_*() Content-Language: en-US To: Yury Norov , Andrew Morton , Minchan Kim , , References: <20220422015839.1274328-1-yury.norov@gmail.com> From: John Hubbard In-Reply-To: <20220422015839.1274328-1-yury.norov@gmail.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.126.230.35] X-ClientProxiedBy: rnnvmail203.nvidia.com (10.129.68.9) To rnnvmail201.nvidia.com (10.129.68.8) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: fccc2cf2-a6fd-420b-cf1f-08da2424e2f0 X-MS-TrafficTypeDiagnostic: DM4PR12MB6301:EE_ X-Microsoft-Antispam-PRVS: X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: V+6Rmvg5VS4FhuKIGDZ6pW+CIQrL945Yni9bUGJK2A1r+jWC6Hwa9FRc+R+K6gXMR+lZ+3Kn1m7g6OyQvvTBzpdWDx1abFGa+/sf0queY0U9GbquWVnYV100B3ZPn2az4HoradbPw5RW+y7tJfIdIIndgLkZWdbIllR/7TgoWIPjx0sRM67qe8quOlSTNbEfjZzPA0lyohKXeXi6zyboSWKkeRYZU3SxadW/+NzqMUAVc3rFA9Cqbeb/dyA/ifABRe1ngxyT12eszFlLcBW55QuCnBD21Bdk3mBOvXOLobnBIZY3sWgtkz0m9AZTEO0/1LDhuGCKQoYtIapPai7bn37UGa2vnWLVxG5qFOqucE+Q1wW8rOeNqfv+4r76hLLp/zI0EQ7DuT6K4rjhoLPqghdt0PxYdhq1YgQwp8ey59kLYhv/EkRp+gE7kz2glBc0lkgJQAiaBCLQrAugKVxg7wmv+JkfMELopRyQIdep30xAJv0aO/+F7oMGvRTJ6jS9LaJVaTWPG0KLd8N2nu54xaAcNILO57ic23QH6YMGNs1i9GSehcxRTpUjJGxnBJ1rkn7FUDoeZfsJZHaZ7XWzg1dOXzHQ2r/XFwRLKwfKPbuu09zY6Suewkd3mqOeehWaS2YRRl9rm39IgNp0EDpvtXivybdtiU7IPI8xXwUj1k6+TgsQ355lJlNfQhLlgMmeZbHzsrb3G131ayn07cD+/G0MI5xZ1y7fvSRcOmihVNCA6qgTzD4fKmMRSzDbDGNoKRXQC0JQ6/S+b6sZjZ0SVPpyoYvXsQNlhKn+y/UO3MiBmc84hpdwWtuqpClne90n1CzHLHFTxBmeLix4JgExxO7bGs4EOFkr36oZ/eVRG6gFdvtjl7GGSz+pu/6k6Jr9/kJWi1aS2lVsyg/Egffejw== X-Forefront-Antispam-Report: CIP:12.22.5.238;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:InfoNoRecords;CAT:NONE;SFS:(13230001)(4636009)(36840700001)(40470700004)(46966006)(26005)(31696002)(966005)(86362001)(53546011)(6666004)(508600001)(2906002)(36860700001)(356005)(5660300002)(81166007)(8936002)(83380400001)(2616005)(40460700003)(70206006)(16526019)(186003)(336012)(47076005)(426003)(316002)(70586007)(110136005)(31686004)(82310400005)(8676002)(36756003)(16576012)(36900700001)(2101003)(43740500002);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 22 Apr 2022 05:56:46.9951 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: fccc2cf2-a6fd-420b-cf1f-08da2424e2f0 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[12.22.5.238];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: DM6NAM11FT004.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR12MB6301 X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: DC4924001A X-Stat-Signature: gqpebeiacsjwe1yzxbj3m6qy3uoi8yw6 Authentication-Results: imf04.hostedemail.com; dkim=pass header.d=Nvidia.com header.s=selector2 header.b=QF0WU3XQ; spf=none (imf04.hostedemail.com: domain of jhubbard@nvidia.com has no SPF policy when checking 40.107.236.78) smtp.mailfrom=jhubbard@nvidia.com; dmarc=pass (policy=reject) header.from=nvidia.com X-HE-Tag: 1650607007-460390 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 4/21/22 18:58, Yury Norov wrote: > pin_user_pages API forces FOLL_PIN in gup_flags, which means that the > API requires struct page **pages to be provided (not NULL). However, the > comment to pin_user_pages() clearly allows for passing in a NULL @pages > argument. > > Remove the incorrect comments, and add WARN_ON_ONCE(!pages) calls to > enforce the API. > > It has been independently spotted by Minchan Kim and confirmed with > John Hubbard: > > https://lore.kernel.org/all/YgWA0ghrrzHONehH@google.com/ > > CC: Minchan Kim > CC: John Hubbard > Signed-off-by: Yury Norov (NVIDIA) > --- Looks good. Please feel free to add: Reviewed-by: John Hubbard thanks, -- John Hubbard NVIDIA > > v1: https://lore.kernel.org/linux-mm/92a2715c-3c98-251d-9195-872d1cf01f9d@nvidia.com/#t > v2: Remove comment for WARN_ON_ONCE() and reword commit message. > > mm/gup.c | 21 +++++++++++++++++---- > 1 file changed, 17 insertions(+), 4 deletions(-) > > diff --git a/mm/gup.c b/mm/gup.c > index f598a037eb04..b1e96b6192de 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -2871,6 +2871,9 @@ int pin_user_pages_fast(unsigned long start, int nr_pages, > if (WARN_ON_ONCE(gup_flags & FOLL_GET)) > return -EINVAL; > > + if (WARN_ON_ONCE(!pages)) > + return -EINVAL; > + > gup_flags |= FOLL_PIN; > return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages); > } > @@ -2893,6 +2896,9 @@ int pin_user_pages_fast_only(unsigned long start, int nr_pages, > */ > if (WARN_ON_ONCE(gup_flags & FOLL_GET)) > return 0; > + > + if (WARN_ON_ONCE(!pages)) > + return 0; > /* > * FOLL_FAST_ONLY is required in order to match the API description of > * this routine: no fall back to regular ("slow") GUP. > @@ -2920,8 +2926,7 @@ EXPORT_SYMBOL_GPL(pin_user_pages_fast_only); > * @nr_pages: number of pages from start to pin > * @gup_flags: flags modifying lookup behaviour > * @pages: array that receives pointers to the pages pinned. > - * Should be at least nr_pages long. Or NULL, if caller > - * only intends to ensure the pages are faulted in. > + * Should be at least nr_pages long. > * @vmas: array of pointers to vmas corresponding to each page. > * Or NULL if the caller does not require them. > * @locked: pointer to lock flag indicating whether lock is held and > @@ -2944,6 +2949,9 @@ long pin_user_pages_remote(struct mm_struct *mm, > if (WARN_ON_ONCE(gup_flags & FOLL_GET)) > return -EINVAL; > > + if (WARN_ON_ONCE(!pages)) > + return -EINVAL; > + > gup_flags |= FOLL_PIN; > return __get_user_pages_remote(mm, start, nr_pages, gup_flags, > pages, vmas, locked); > @@ -2957,8 +2965,7 @@ EXPORT_SYMBOL(pin_user_pages_remote); > * @nr_pages: number of pages from start to pin > * @gup_flags: flags modifying lookup behaviour > * @pages: array that receives pointers to the pages pinned. > - * Should be at least nr_pages long. Or NULL, if caller > - * only intends to ensure the pages are faulted in. > + * Should be at least nr_pages long. > * @vmas: array of pointers to vmas corresponding to each page. > * Or NULL if the caller does not require them. > * > @@ -2976,6 +2983,9 @@ long pin_user_pages(unsigned long start, unsigned long nr_pages, > if (WARN_ON_ONCE(gup_flags & FOLL_GET)) > return -EINVAL; > > + if (WARN_ON_ONCE(!pages)) > + return -EINVAL; > + > gup_flags |= FOLL_PIN; > return __gup_longterm_locked(current->mm, start, nr_pages, > pages, vmas, gup_flags); > @@ -2994,6 +3004,9 @@ long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages, > if (WARN_ON_ONCE(gup_flags & FOLL_GET)) > return -EINVAL; > > + if (WARN_ON_ONCE(!pages)) > + return -EINVAL; > + > gup_flags |= FOLL_PIN; > return get_user_pages_unlocked(start, nr_pages, pages, gup_flags); > }