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 BED9EC38A2D for ; Fri, 21 Oct 2022 20:48:22 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 52E518E0002; Fri, 21 Oct 2022 16:48:22 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 48FD88E0001; Fri, 21 Oct 2022 16:48:22 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2E2D18E0002; Fri, 21 Oct 2022 16:48:22 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 196B88E0001 for ; Fri, 21 Oct 2022 16:48:22 -0400 (EDT) Received: from smtpin05.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id E7645A1359 for ; Fri, 21 Oct 2022 20:48:21 +0000 (UTC) X-FDA: 80046144402.05.D207BBC Received: from mx0b-00069f02.pphosted.com (mx0b-00069f02.pphosted.com [205.220.177.32]) by imf11.hostedemail.com (Postfix) with ESMTP id 5C4B040004 for ; Fri, 21 Oct 2022 20:48:21 +0000 (UTC) Received: from pps.filterd (m0246631.ppops.net [127.0.0.1]) by mx0b-00069f02.pphosted.com (8.17.1.5/8.17.1.5) with ESMTP id 29LKVK7W007815; Fri, 21 Oct 2022 20:48:20 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=date : from : to : cc : subject : message-id : references : content-type : in-reply-to : mime-version; s=corp-2022-7-12; bh=JtADH1H2H7g+5eIYCoyCXBJl9xpoG7bwNEK203ZUgnI=; b=zIqPKAYaPclHKeHX7AlXz2zaMyjuuS2LKe0Ab7/afCHI11Oj6EeoW4fSPoHUr2pdiLPq 4YSnOvQQg2+fCvwfuvGCEuSt8Lz+tqhE3aaP5lqsVN9RjkO0WlHdmxacX1OJdvExhTX8 2mp3WoWCzqfi83Dxn2M/U+aYBr7XCTjSFW/3F5O7Mrbk9jEt0HyXky08KY5+rxcbqkwj bUUQuHsHJHQGDMlMkgBHfc8J5AXO3lB0YY+sYExo1n0R5gzo/XZBquUrcdYIy90kAFjW 06YScG8P3O7abN3tsjRIQMeeu3aQg+vP+Ek9PdljHiNMujtuEum+GiL4jCMwls/DR+lj wQ== Received: from phxpaimrmta01.imrmtpd1.prodappphxaev1.oraclevcn.com (phxpaimrmta01.appoci.oracle.com [138.1.114.2]) by mx0b-00069f02.pphosted.com (PPS) with ESMTPS id 3k7mw3sub4-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 21 Oct 2022 20:48:20 +0000 Received: from pps.filterd (phxpaimrmta01.imrmtpd1.prodappphxaev1.oraclevcn.com [127.0.0.1]) by phxpaimrmta01.imrmtpd1.prodappphxaev1.oraclevcn.com (8.17.1.5/8.17.1.5) with ESMTP id 29LIVwYX038611; Fri, 21 Oct 2022 20:48:19 GMT Received: from nam10-bn7-obe.outbound.protection.outlook.com (mail-bn7nam10lp2106.outbound.protection.outlook.com [104.47.70.106]) by phxpaimrmta01.imrmtpd1.prodappphxaev1.oraclevcn.com (PPS) with ESMTPS id 3k8hr3k1xv-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 21 Oct 2022 20:48:19 +0000 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=MDtKf+Q4OUPfhIQdTZUo0lB+ZJnHVwfIjbn54FHicO7tMNm0GJbYzcEEDTsWMp/3eSYCE8F9iNFMvFeLiLtOdImdulkMiRvqQ2mQtf+4oVsHA2facVrxWGxdH9sFo/3ODtEY3RZZS8uslMlJ9xl+mvRhOg+AEVY5TvCr03HhVgD53BsOzBP9aGUgj7/Jicy6FJ/SPCwzQqZpK1FpZqzU9Y+jXuhtbii1LmYLSYApkBoJtMpYFbp9fjBN/OsylcPssqy0UNlEgnJIX0Ni1rcWrAOnB1i1Az0qbEearQHJdVQ9zsBPV8FDKMSKuWB5xOw8rn9KzxsHkzcQofn7gyD7xg== 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=JtADH1H2H7g+5eIYCoyCXBJl9xpoG7bwNEK203ZUgnI=; b=ju62kyCtQl4HIeGI3AFHF383mHltGUbf2unAaIg7jsbNMOAmtFJOaGXxDDNK/T9YPI59+t/qBCd3C1yRyqqYVhCpsX1wPKh74wqRvr8Lt7CHNz93GNt9P00BzgXFO4yXUVwyuIUjRb7sC6SfVyVOS3a6oL7vPqlXKUI3FlRrB1APpwXvwSStrG7u4aBcM11OUzzGrI0n9JjfNYWjC+AJrSp+azip2Dj06SZbLW/ozt51tLlUhOhzoILQiKM4MkecJFoh9mKRNKSi89ZjeronXsXBASjFv+8nGq1yZxk41Cqix5CwTqmzvvHxEP+6qm2nB/Z4/HdJ7koNXkNi6DmxFA== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=oracle.com; dmarc=pass action=none header.from=oracle.com; dkim=pass header.d=oracle.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.onmicrosoft.com; s=selector2-oracle-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=JtADH1H2H7g+5eIYCoyCXBJl9xpoG7bwNEK203ZUgnI=; b=HROvzhADRPw+a4deIV/1870hNDgqtQ08Cw4WPJhSh1ddu7p/1CmmPFZR9VGABQDPrLIg2752lP2p6nQmtFI4Wdb5IDEVqSe174pg2rlPRAH5RmFgdYiPaw91HVotkL4vWFM3HVejKN8hX1l+PztzKPNH5KwmJ1iD+7lkAvmmpEM= Received: from BY5PR10MB4196.namprd10.prod.outlook.com (2603:10b6:a03:20d::23) by SJ0PR10MB4687.namprd10.prod.outlook.com (2603:10b6:a03:2d8::12) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.5746.21; Fri, 21 Oct 2022 20:48:17 +0000 Received: from BY5PR10MB4196.namprd10.prod.outlook.com ([fe80::5f85:c22e:b7fa:21bd]) by BY5PR10MB4196.namprd10.prod.outlook.com ([fe80::5f85:c22e:b7fa:21bd%5]) with mapi id 15.20.5746.021; Fri, 21 Oct 2022 20:48:17 +0000 Date: Fri, 21 Oct 2022 13:48:14 -0700 From: Mike Kravetz To: Rik van Riel Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel-team@meta.com, Andrew Morton , David Hildenbrand Subject: Re: [PATCH] mm,madvise,hugetlb: fix unexpected data loss with MADV_DONTNEED on hugetlbfs Message-ID: References: <20221021154546.57df96db@imladris.surriel.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221021154546.57df96db@imladris.surriel.com> X-ClientProxiedBy: MW4PR03CA0202.namprd03.prod.outlook.com (2603:10b6:303:b8::27) To BY5PR10MB4196.namprd10.prod.outlook.com (2603:10b6:a03:20d::23) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BY5PR10MB4196:EE_|SJ0PR10MB4687:EE_ X-MS-Office365-Filtering-Correlation-Id: 852a4d84-4a98-4a0d-47f4-08dab3a59473 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:BY5PR10MB4196.namprd10.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230022)(7916004)(39860400002)(346002)(136003)(376002)(366004)(396003)(451199015)(4326008)(66476007)(8936002)(44832011)(41300700001)(8676002)(66946007)(6916009)(54906003)(316002)(66556008)(5660300002)(86362001)(966005)(38100700002)(478600001)(6666004)(6486002)(186003)(83380400001)(6512007)(26005)(9686003)(6506007)(53546011)(33716001)(2906002);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?uU8lbWPOdtGbw1uz4Pl3c8li5hMmQKeVHqYXM87xXSJ5tS4BiY36gELZwMWQ?= =?us-ascii?Q?96uMeCRPWoFeoenL3fPUEJgdZYy8ynESQRJkE1pNgPxSK+s6E+dtRplrd849?= =?us-ascii?Q?qE/Ahssytj2nJymww4Ase0tjRRXYFyivgVMEbJ34bkO/qZJRC4B5HwfuT57w?= =?us-ascii?Q?8+TrLdA72/r+bdn//TOH4Pp5t9TV9c9ZZJcxd88f+2kiQlXdVx/7KnSdiOzu?= =?us-ascii?Q?YA8AvJ9aegaa/G8G0zkoEo+naDJRes/uuQS7RZPYIzmVWs0NiO7BAZItzgiY?= =?us-ascii?Q?mPuINHSPgV4+8vaLz+MyEt65/eY5DuidLt0NuM+E4olCXXux9Rj8j03McQSq?= =?us-ascii?Q?YyTWu8jsxBUjjEIgb1JBG9D/wa8uxD0OyK/C7UjsgWZb1B9O7cO+2+gV/J5Q?= =?us-ascii?Q?2MZwztABKsb8D1TBIbOOVk0B+FZ2a8y108Xb644k0nqvyXaT+56qLckL4HxX?= =?us-ascii?Q?Li+X+Lxxk0JJ678i6h50RHqoTMHxbBHvP04ev/PYFWoOnvEpQlepAnaxZFAI?= =?us-ascii?Q?GRw9tXKXqYmpZEVFz2gCrTBOosfc93CMg4BmnqvSWjr6sO/VHEo3LViw+PJJ?= =?us-ascii?Q?Iik1KJwJ9OVBL03/rHS2cukC+vWnNGaB7XfzCMgc/0TYK6aiRAIOC1cbZVQR?= =?us-ascii?Q?x0TTdioVpvvRxJrYYfAp57rXlLnn6/ZkPL6gGTxCEVfkp5jqX6VKB9emZwMg?= =?us-ascii?Q?rc1ObJv69hI77N+tIv67Sc/EW+lClMifiOJFGuREczzjLVfpdEXFXEm8YRDB?= =?us-ascii?Q?kTeBy+md5uGpvuTjMEm5o+wbToBngSGsHdm70yod2ZcycfGwNT+1U0Mh/igq?= =?us-ascii?Q?cXbvObXN6GlkIsAZWlLziJai2+G15gUzi9qaLl0jtThQxKPHeY08TSGnn97Z?= =?us-ascii?Q?2lNYH1WmrJ36z3x0PK5LtHdFLedh9fN2o5DYOCo1Fw24NQYjtWXAZdb/FVHb?= =?us-ascii?Q?/Am3LxvdM42oYPkR2R3oVHyYBx+OUuBBpXNmnc7yIBxdFYZFbJHxYMK/kpiW?= =?us-ascii?Q?gXDkcAK+9yFpvoGQILElwgdSsUecbyP+bOnr/6qJX44WXpQqdP5fY5yhOfEz?= =?us-ascii?Q?JwB3IGKN+5S6IkrRFDPAQyOVSfGEZiPlulrCMtMlXW/3cWne1y3eibG5t8Sz?= =?us-ascii?Q?j0rmbbeTuWNCnwTrwQFvWI7+aIbHRBdZIE7cDClHMsq1u7G9YrVdXByQpuLY?= =?us-ascii?Q?2XRLzGbqgSkyAHJ1jTO+YnR9MhbbzCVvzxhEc3qm7ulMfXHkoABMdFF9f1xz?= =?us-ascii?Q?i/x+idYfeMvhXzP+CYxVhFzI8sSvqOsZhckbxJUPPVnZO7KnD5Yu8dG7D0aU?= =?us-ascii?Q?j4bYuVmZtH4Abk8Hi6DQGG+ntW53t/Rg7aN01dTGReD9uKT14Z165Umov+1r?= =?us-ascii?Q?yoIeAP430bRjlUqSyg+pUdr0SJP9ytw77igTYdOXcYXVOUEmAGXS62jhOuH0?= =?us-ascii?Q?c5goFW7u9xcFz7hOJc9dkZVyWov3A9LHjkjp0WEPFuxUgIczpZ6RnjBR828D?= =?us-ascii?Q?6kIDLCIgQT9o0Hyr/s5Pco30KeZH2fxo+N6bP80cOYEVIqehGuuogryZf8bO?= =?us-ascii?Q?sNSBJ23Xk5u9be3CDieg7ZaIyECofcrD0sUAKtL42RH2teJOxHP1TbcQe/22?= =?us-ascii?Q?Lg=3D=3D?= X-OriginatorOrg: oracle.com X-MS-Exchange-CrossTenant-Network-Message-Id: 852a4d84-4a98-4a0d-47f4-08dab3a59473 X-MS-Exchange-CrossTenant-AuthSource: BY5PR10MB4196.namprd10.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 21 Oct 2022 20:48:16.9937 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: RNeqhG296DOBUTclyiqNN0YACNbFQp6ZRZxYxjXdm7BndUhtociOKHZ6S7xUAIAGG7p6M4KgzP1jXRt2+MIjHw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ0PR10MB4687 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.895,Hydra:6.0.545,FMLib:17.11.122.1 definitions=2022-10-21_04,2022-10-21_01,2022-06-22_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 adultscore=0 bulkscore=0 malwarescore=0 phishscore=0 mlxlogscore=999 spamscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2209130000 definitions=main-2210210121 X-Proofpoint-ORIG-GUID: T5-cPBY47vmySqKH89bLHL7Orn3gYMq0 X-Proofpoint-GUID: T5-cPBY47vmySqKH89bLHL7Orn3gYMq0 ARC-Seal: i=2; s=arc-20220608; d=hostedemail.com; t=1666385301; a=rsa-sha256; cv=pass; b=gojBkpZUenMsjXyqAAw4m2N6mpgo3ghEbSRvSmFv8tkXQdQ8oC8+OEQpk9Oy3AGfLUcjp3 JHLM06m9Iy+1SmMRbG2qE5BMIS6ba2jgwLOiXZWkkiKEwHf8fhb+du3YukoE3j0qoFqK+W aDYe/HD9gXev8rxcEAWB8U3AypQkRXw= ARC-Authentication-Results: i=2; imf11.hostedemail.com; dkim=pass header.d=oracle.com header.s=corp-2022-7-12 header.b=zIqPKAYa; dkim=pass header.d=oracle.onmicrosoft.com header.s=selector2-oracle-onmicrosoft-com header.b=HROvzhAD; spf=pass (imf11.hostedemail.com: domain of mike.kravetz@oracle.com designates 205.220.177.32 as permitted sender) smtp.mailfrom=mike.kravetz@oracle.com; arc=pass ("microsoft.com:s=arcselector9901:i=1"); dmarc=pass (policy=none) header.from=oracle.com ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1666385301; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=JtADH1H2H7g+5eIYCoyCXBJl9xpoG7bwNEK203ZUgnI=; b=ROsdGhbEnzcaU/n/Gyax8CrKngbB2Ly7rxJ0O/sTTTi+6xOzVcfirv4mw9JfwWXLBeR/UN KzSZ8i/8CYwb8fEqsoDeQFHLgkhiRnGM1/M4xToir30TaKiafgR50JaARlziCMv7Xl5491 DFfQzQCdQ80urhiv0mo5p8Js7NeR00o= Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=oracle.com header.s=corp-2022-7-12 header.b=zIqPKAYa; dkim=pass header.d=oracle.onmicrosoft.com header.s=selector2-oracle-onmicrosoft-com header.b=HROvzhAD; spf=pass (imf11.hostedemail.com: domain of mike.kravetz@oracle.com designates 205.220.177.32 as permitted sender) smtp.mailfrom=mike.kravetz@oracle.com; arc=pass ("microsoft.com:s=arcselector9901:i=1"); dmarc=pass (policy=none) header.from=oracle.com X-Stat-Signature: tdj8ma7imr4aicreahnjebyt1a544udq X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 5C4B040004 X-Rspam-User: X-HE-Tag: 1666385301-69493 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 10/21/22 15:45, Rik van Riel wrote: > A common use case for hugetlbfs is for the application to create > memory pools backed by huge pages, which then get handed over to > some malloc library (eg. jemalloc) for further management. > > That malloc library may be doing MADV_DONTNEED calls on memory > that is no longer needed, expecting those calls to happen on > PAGE_SIZE boundaries. > Thanks Rik. I tend to agree with this direction as it is 'breaking' current code. David and I discussed this in this thread, https://lore.kernel.org/linux-mm/356a4b9a-1f56-ae06-b211-bd32fc93ecda@redhat.com/ One thing to note is that there was not any documentation saying madvise would happen on page boundaries. The system call takes a length and rounds up to page size. However, the man page explicitly said it operates on a byte range. Certainly mm people and others know we only operate on pages. But, that is not what was documented. When the change was made to add hugetlb support, the decision was made to round up the range to hugetlb page boundaries in hugetlb vmas. This was to be consistent with how madvise operated on base pages. At the same time, madvise documentation was updated say it operates on page boundaries as well as the behavior for hugetlb mappings. If moving forward with this change we will need to update the man page. -- Mike Kravetz > However, currently the MADV_DONTNEED code rounds up any such > requests to HPAGE_PMD_SIZE boundaries. This leads to undesired > outcomes when jemalloc expects a 4kB MADV_DONTNEED, but 2MB of > memory get zeroed out, instead. > > Use of pre-built shared libraries means that user code does not > always know the page size of every memory arena in use. > > Avoid unexpected data loss with MADV_DONTNEED by rounding up > only to PAGE_SIZE (in do_madvise), and rounding down to huge > page granularity. > > That way programs will only get as much memory zeroed out as > they requested. > > While we're here, refactor madvise_dontneed_free_valid_vma > a little so mlocked hugetlb VMAs need MADV_DONTNEED_LOCKED. > > Cc: Mike Kravetz > Cc: Andrew Morton > Cc: David Hildenbrand > Fixes: 90e7e7f5ef3f ("mm: enable MADV_DONTNEED for hugetlb mappings") > --- > mm/madvise.c | 26 +++++++++++++++++++------- > 1 file changed, 19 insertions(+), 7 deletions(-) > > diff --git a/mm/madvise.c b/mm/madvise.c > index 2baa93ca2310..a60e8e23c323 100644 > --- a/mm/madvise.c > +++ b/mm/madvise.c > @@ -799,21 +799,29 @@ static bool madvise_dontneed_free_valid_vma(struct vm_area_struct *vma, > unsigned long *end, > int behavior) > { > - if (!is_vm_hugetlb_page(vma)) { > - unsigned int forbidden = VM_PFNMAP; > + unsigned int forbidden = VM_PFNMAP; > > - if (behavior != MADV_DONTNEED_LOCKED) > - forbidden |= VM_LOCKED; > + if (behavior != MADV_DONTNEED_LOCKED) > + forbidden |= VM_LOCKED; > > - return !(vma->vm_flags & forbidden); > - } > + if (vma->vm_flags & forbidden) > + return false; > + > + if (!is_vm_hugetlb_page(vma)) > + return true; > > if (behavior != MADV_DONTNEED && behavior != MADV_DONTNEED_LOCKED) > return false; > if (start & ~huge_page_mask(hstate_vma(vma))) > return false; > > - *end = ALIGN(*end, huge_page_size(hstate_vma(vma))); > + /* > + * Madvise callers expect the length to be rounded up to the page > + * size, but they may not know the page size for this VMA is larger > + * than PAGE_SIZE! Round down huge pages to avoid unexpected data loss. > + */ > + *end = ALIGN_DOWN(*end, huge_page_size(hstate_vma(vma))); > + > return true; > } > > @@ -828,6 +836,10 @@ static long madvise_dontneed_free(struct vm_area_struct *vma, > if (!madvise_dontneed_free_valid_vma(vma, start, &end, behavior)) > return -EINVAL; > > + /* A small MADV_DONTNEED on a huge page gets rounded down to zero. */ > + if (start == end) > + return 0; > + > if (!userfaultfd_remove(vma, start, end)) { > *prev = NULL; /* mmap_lock has been dropped, prev is stale */ > > -- > 2.37.2 > >