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=-14.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,MSGID_FROM_MTA_HEADER,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 2F1F1C433F5 for ; Thu, 9 Sep 2021 05:51:02 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id AEE0660FE3 for ; Thu, 9 Sep 2021 05:51:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org AEE0660FE3 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=fb.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 22AC2900002; Thu, 9 Sep 2021 01:51:01 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 1DB796B0072; Thu, 9 Sep 2021 01:51:01 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 02D2F900002; Thu, 9 Sep 2021 01:51:00 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0132.hostedemail.com [216.40.44.132]) by kanga.kvack.org (Postfix) with ESMTP id E642A6B0071 for ; Thu, 9 Sep 2021 01:51:00 -0400 (EDT) Received: from smtpin26.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 8911318338081 for ; Thu, 9 Sep 2021 05:51:00 +0000 (UTC) X-FDA: 78566961480.26.BFEF520 Received: from mx0b-00082601.pphosted.com (mx0b-00082601.pphosted.com [67.231.153.30]) by imf09.hostedemail.com (Postfix) with ESMTP id 0AD283000100 for ; Thu, 9 Sep 2021 05:50:59 +0000 (UTC) Received: from pps.filterd (m0109332.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.43/8.16.0.43) with SMTP id 1895TW6x025201; Wed, 8 Sep 2021 22:50:41 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=subject : to : cc : references : from : message-id : date : in-reply-to : content-type : content-transfer-encoding : mime-version; s=facebook; bh=1148QoFJ7VL6Moki25eFGTbOe7hPlHsHwFLkPlFSONo=; b=ftd3ag9PBe7Vll4PFhb41C8MRAmxDN1zCFwp+gyM0S8ZbLPHLEB972qalt3zlNevocy8 ePUoxWJ0AZedjO0a+PY7EiLteG2SfRfAAM+FtSudWAzWyQQYB7vvVch/PAqfIG8/WjuP YrLgLwZG8Q13xl9s50SF4rn7FzwZSPrE29E= Received: from mail.thefacebook.com ([163.114.132.120]) by mx0a-00082601.pphosted.com with ESMTP id 3ay5vk2eu8-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT); Wed, 08 Sep 2021 22:50:41 -0700 Received: from NAM10-MW2-obe.outbound.protection.outlook.com (100.104.98.9) by o365-in.thefacebook.com (100.104.94.198) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.14; Wed, 8 Sep 2021 22:50:39 -0700 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=BUB9xyNtDskB151bH0b+6OlJyC/TBOQuoImC9uXkK91vW1UYNN/qk4JWHrCH8On7Hwsb52lduoui7KfCnugxX3qrGc5jW3k2Poi9sf7FHfDiJsxYSStHidQjoK1+8O1ksOCuZdmVQ1G3FhrDXKcSyvqb2INaVl9rfda2B+PMIpTEGo91BoU1J7rRADIvGaEJUavsY551OZt3ZOyQhSEpHO3P47Z76Fyj9biV4D1b3Rr2yDYBsxk4YPhg6C1xYL70IUhDGvSuQPlJt9agZARPNaphyoM1QJ+eB8j3Mrr1XHosnA9bxQiF4RSrZ7UkL4bNFCFqirKBwF/9mkaLOC4OvQ== 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; bh=1148QoFJ7VL6Moki25eFGTbOe7hPlHsHwFLkPlFSONo=; b=ISuoF6qHTsX7P31mFA0XW7o3mppEZOhvrGJ9UXJjwy5s8wf91dlZILF5je6PFLwOdFtx2Mn63uTG9Hu44a0Y3XT9H4NK0reWVVQplaEt1pa81tHWSupgysRXrV0BSA4QNz29I22HIUa84EO+95Lhrn3HibAul9hBWix2GJbNs8fHMOgiSAc64D+MF6f+B4Hc3igfcUSlL7PO8YF0egivRkw1nZ00rQCY+goLEIqenAkJz53VVowinG1pOyFHASgYFcctFwmSX44m7pUgsTlpyaZvKa1vCtUJlJRKVvChaq3eB8rz7ovzQfEoo/2pO+DBq5GNoYjkhKns8V5CtszPiA== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=fb.com; dmarc=pass action=none header.from=fb.com; dkim=pass header.d=fb.com; arc=none Received: from SN6PR1501MB2064.namprd15.prod.outlook.com (2603:10b6:805:d::27) by SA1PR15MB4901.namprd15.prod.outlook.com (2603:10b6:806:1d0::7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4500.16; Thu, 9 Sep 2021 05:50:38 +0000 Received: from SN6PR1501MB2064.namprd15.prod.outlook.com ([fe80::51ef:4b41:5aea:3f75]) by SN6PR1501MB2064.namprd15.prod.outlook.com ([fe80::51ef:4b41:5aea:3f75%6]) with mapi id 15.20.4500.016; Thu, 9 Sep 2021 05:50:38 +0000 Subject: Re: [PATCH mm/bpf v2] mm: bpf: add find_vma_no_check() without lockdep_assert on mm->mmap_lock To: Jason Gunthorpe CC: Liam Howlett , Alexei Starovoitov , Andrew Morton , Luigi Rizzo , Peter Zijlstra , Daniel Borkmann , bpf , "linux-mm@kvack.org" , Alexei Starovoitov , Andrii Nakryiko , "kernel-team@fb.com" , "walken@fb.com" References: <20210908172118.n2f4w7epm6hh62zf@ast-mbp.dhcp.thefacebook.com> <20210908105259.c47dcc4e4371ebb5e147ee6e@linux-foundation.org> <20210908180258.yjh62e5oouckar5b@ast-mbp.dhcp.thefacebook.com> <20210908111527.9a611426e257d55ccbbf46eb@linux-foundation.org> <20210908183032.zoh6dj5xh455z47f@revolver> <20210908184912.GA1200268@ziepe.ca> <7aece51f-141c-db55-5d4c-8c6658b6a1fc@fb.com> <20210908233331.GA3544071@ziepe.ca> From: Yonghong Song Message-ID: <18766a42-ea2f-e019-a8f7-43db50870300@fb.com> Date: Wed, 8 Sep 2021 22:50:35 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 In-Reply-To: <20210908233331.GA3544071@ziepe.ca> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: BY5PR16CA0010.namprd16.prod.outlook.com (2603:10b6:a03:1a0::23) To SN6PR1501MB2064.namprd15.prod.outlook.com (2603:10b6:805:d::27) MIME-Version: 1.0 Received: from [IPv6:2620:10d:c085:21d6::108f] (2620:10d:c090:400::5:fa3d) by BY5PR16CA0010.namprd16.prod.outlook.com (2603:10b6:a03:1a0::23) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4500.14 via Frontend Transport; Thu, 9 Sep 2021 05:50:37 +0000 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 86efaf83-a137-4a65-b12c-08d97355bff4 X-MS-TrafficTypeDiagnostic: SA1PR15MB4901: X-MS-Exchange-Transport-Forked: True X-Microsoft-Antispam-PRVS: X-FB-Source: Internal X-MS-Oob-TLC-OOBClassifiers: OLM:7691; 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:SN6PR1501MB2064.namprd15.prod.outlook.com;PTR:;CAT:NONE;SFS:(4636009)(366004)(508600001)(6486002)(38100700002)(5660300002)(53546011)(31696002)(186003)(54906003)(31686004)(86362001)(2906002)(52116002)(8676002)(4326008)(6916009)(36756003)(316002)(2616005)(7416002)(8936002)(66946007)(83380400001)(66556008)(66476007)(43740500002)(45980500001);DIR:OUT;SFP:1102; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?UUpCOCtJVDZTOG9SSnVNTVBEa0orUlVvNkJIZUdHZm05WUhiREV4SGtBYUQ3?= =?utf-8?B?MzJSSElXTG04RUNyOGd6NWxSQ3diRlAzNExydjl6UzRJb096MmRVS0Q3TlVt?= =?utf-8?B?eUhKeHZsbHFNSEpzRFpjZ3FBRnRNNGw4aFNMR3ZmcGllMkZnRlFKem5RNmZn?= =?utf-8?B?TEdkTVZFQkNiNk1nQ2I1RjBOdVVyU0t3cDEzWmIyN3BsWk9peXJidGxIUmFC?= =?utf-8?B?MEZKMkhaNzZNMUFnVlFQTlcxaENjSnFGcTBpUHJVdmYrQk05QUs2dG8yRVlN?= =?utf-8?B?cytlSy9VdVE2UDFzL0ZnTUFRd29INVdhcE1FeDFDR2VUQlhHbTgvbll1bzBR?= =?utf-8?B?UnJncmtQcTZzMzBtR1ExRTJ0S0ZwbmVjSHlnQS9CSXQyeFBhbVpjYU40aDRw?= =?utf-8?B?a2dqN2kzbkVsV0k4Z0FFdldwQ0hpdUtzRUVOSkdFUGxwR21ZL2lwZGw3SDUz?= =?utf-8?B?SnJrYUE4WStTbmkzZHN2dEMvOXlVaXVPd1VIR09qQzFvNVowOHZ3ZUZIUWN1?= =?utf-8?B?Y21nWWx5Zm9QQnpEUWt2aVJLYW9xSVdEc1JZcy9JTzQvUGdreHFNNGRacC9z?= =?utf-8?B?MEZuR2ZmT3pHL3BYNVp0WGMwSG40UmtYbTA0YXNheGd5LzNOTTBpUDhnMjNY?= =?utf-8?B?aVZRNnpIcWU0SmN1U3JZMncyRENYUVdPVXFDdm55c1A4Wkt0NUdpbFIvdTA1?= =?utf-8?B?WWRjdCszdEp6b3I5SzhXbWI5ZTdRZTZUaE9odFdGZU1CTVh3cjZOa0I5SUVu?= =?utf-8?B?c0RQREdKM253bERvSGdzeGdlQUNYeFFMcTNrU3BZMFlMSVhDdXNDWEJGT3By?= =?utf-8?B?WjJURitqK21NTHJWMmRNUHRHWXpRT1lNdFJUNlkyTVI4blF1eHZ2Y2FTWXdL?= =?utf-8?B?NGFkM3hjR28wamRKbXNYRHZwYS83am9YTzhoLzRRa3d3S0duNFZEdS82Q24z?= =?utf-8?B?NWFGbnhIblVwN1F4alFHQ2lMdjdxclo1UEw0d3RYNy9idk5wQUxGdHdoUnA0?= =?utf-8?B?dmZ2TEROVDdUMGd0Y3dXYjhyUDE0WnJVVndqb21SVXU2R1hQOEZGVGY4UVFp?= =?utf-8?B?Y01DZFlubjRGSElXSjNoT3BDdTJOVmxkaFRXbHA4dXc0emJDeGNlQjVnb2xz?= =?utf-8?B?a0d1Ukt3aVZrMU5FS2dpZE5ibXVXN2tGUEJxRzZWSHU1dnBEeEFNL2pleE5k?= =?utf-8?B?NmVVRWx1akhvTWpYU0JQRlFENFBGbGR2UUdPSHZFSGZHU0lqS2dZM21FczFj?= =?utf-8?B?bVZsNHVtdklzK3kzSHgvMEVxeTYxS0RqZXVneVUwSmU5K2VkRzZtYmszSk9v?= =?utf-8?B?KytaMnpZb0U4eU1pd3VZTUs5VFpoblppb25WWGlscVZ3SmY4a0VaUG5iZTZU?= =?utf-8?B?Mk5sSi85ZDB1RUxnSEZwTkdXS3lPdVpJL2k0REtCNy9iOVNoTkdiTlliNm9q?= =?utf-8?B?NXoySHBpZVR0VUxiZzNPVE9nZTlYb3JTT0VPcm52N3pncHZmajB6dkVaQXZq?= =?utf-8?B?MCs3cmI4MGtXbjh3WDhxa0IrTVh4Q09pWVJnOEdCUEVmZXF3bUF0RkVzdFhi?= =?utf-8?B?LzFZTWp3cTRiRWxKeFBTZ2svTkppTkt5ck1EdGRlakdvdjZRcHd4Z0lZRkJZ?= =?utf-8?B?eW8yTDRHc2ZNend4NWRqWG1pemF6dmN4UVpNdTV2Q05rYW1NejA3NFJ4N2ZQ?= =?utf-8?B?Vi9CbzVFV2V1Yis1b1JsOHFyRFovV0lHNnZ6dUN4V0kyNW9CM3NQa0FXdUpO?= =?utf-8?B?c0h4Nzg4eXlmNEh6aDQ3UmloQ0cvc2gwTnVHMXJseExjQVlOdmhNbXJaNERB?= =?utf-8?Q?BY5b/wL95lPTqbORQ2CHqu+6vH/tniVFwa6O8=3D?= X-MS-Exchange-CrossTenant-Network-Message-Id: 86efaf83-a137-4a65-b12c-08d97355bff4 X-MS-Exchange-CrossTenant-AuthSource: SN6PR1501MB2064.namprd15.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 09 Sep 2021 05:50:38.0813 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: YVt6yqUTXadtRpXGojT7wHO3QqdCWj5v/dA6vY7LAP6nc23WKUJUKvA50r/VGy9G X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA1PR15MB4901 X-OriginatorOrg: fb.com X-Proofpoint-GUID: Cp2GAwIoW7ENyIJikDjMPp4eug61mz6Z X-Proofpoint-ORIG-GUID: Cp2GAwIoW7ENyIJikDjMPp4eug61mz6Z X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.790 definitions=2021-09-09_01:2021-09-07,2021-09-09 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 malwarescore=0 lowpriorityscore=0 mlxscore=0 adultscore=0 bulkscore=0 spamscore=0 suspectscore=0 priorityscore=1501 phishscore=0 impostorscore=0 mlxlogscore=999 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2109030001 definitions=main-2109090033 X-FB-Internal: deliver X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 0AD283000100 Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=fb.com header.s=facebook header.b=ftd3ag9P; dmarc=pass (policy=reject) header.from=fb.com; spf=pass (imf09.hostedemail.com: domain of "prvs=88868e9a87=yhs@fb.com" designates 67.231.153.30 as permitted sender) smtp.mailfrom="prvs=88868e9a87=yhs@fb.com" X-Stat-Signature: tu8brnb7q8qbfbofqkjdtj4hsju3mtdd X-HE-Tag: 1631166659-543079 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 9/8/21 4:33 PM, Jason Gunthorpe wrote: > On Wed, Sep 08, 2021 at 12:11:54PM -0700, Yonghong Song wrote: >> >> >> On 9/8/21 11:49 AM, Jason Gunthorpe wrote: >>> On Wed, Sep 08, 2021 at 06:30:52PM +0000, Liam Howlett wrote: >>> >>>> /* Look up the first VMA which satisfies addr < vm_end, NULL if none. */ >>>> -struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr) >>>> +struct vm_area_struct *find_vma_non_owner(struct mm_struct *mm, >>>> + unsigned long addr) >>>> { >>>> struct rb_node *rb_node; >>>> struct vm_area_struct *vma; >>>> - mmap_assert_locked(mm); >>>> + VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_lock), mm); >>>> /* Check the cache first. */ >>>> vma = vmacache_find(mm, addr); >>>> if (likely(vma)) >>>> @@ -2325,6 +2326,11 @@ struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr) >>>> return vma; >>>> } >>>> +struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr) >>>> +{ >>>> + lockdep_assert_held(&mm->mmap_lock); >>>> + return find_vma_non_owner(mm, addr); >>>> +} >>>> EXPORT_SYMBOL(find_vma); >>>> /* >>>> >>>> >>>> Although this leaks more into the mm API and was referred to as ugly >>>> previously, it does provide a working solution and still maintains the >>>> same level of checking. >>> >>> I think it is no better than before. >>> >>> The solution must be to not break lockdep in the BPF side. If Peter's >>> reworked algorithm is not OK then BPF should drop/acquire the lockdep >>> when it punts the unlock to the WQ. >> >> The current warning is triggered by bpf calling find_vma(). > > Yes, but that is because the lockdep has already been dropped. > > It looks to me like it basically does this: > > mmap_read_trylock_non_owner(current->mm) > > vma = find_vma(current->mm, ips[i]); > > if (!work) { > mmap_read_unlock_non_owner(current->mm); > } else { > work->mm = current->mm; > irq_work_queue(&work->irq_work); > > > And the only reason for this lockdep madness is because the > irq_work_queue() does: > > static void do_up_read(struct irq_work *entry) > { > struct stack_map_irq_work *work; > > if (WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_RT))) > return; > > work = container_of(entry, struct stack_map_irq_work, irq_work); > mmap_read_unlock_non_owner(work->mm); > } > > > This is all about deferring the unlock to outside an IRQ context. The > lockdep ownership is transfered from the IRQ to the work, which is > something that we don't usually do or model in lockdep. > > Lockdep complains with the straightforward code because exiting an IRQ > with locks held is illegal. > > The saner version is more like: > > mmap_read_trylock(current->mm) > > vma = find_vma(current->mm, ips[i]); > > if (!work) { > mmap_read_unlock(current->mm); > } else { > work->mm = current->mm; > the lock held> > rwsem_release(&mm->mmap_lock.dep_map, _RET_IP_); > irq_work_queue(&work->irq_work); > > > do_up_read(): > > mmap_read_unlock_non_owner(work->mm); > > ie properly model in lockdep that ownership moves from the IRQ to the > work. At least we don't corrupt the core mm code with this insanity. Thanks for the suggestion! I verified the above change indeed work. Will send v4 soon. > > Jason >