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V" , Andrea Arcangeli , "Kirill A . Shutemov" , Davidlohr Bueso , Prakash Sangappa , James Houghton , Mina Almasry , Pasha Tatashin , Axel Rasmussen , Ray Fucillo , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 6/8] hugetlb: add vma based lock for pmd sharing Message-ID: References: <20220824175757.20590-1-mike.kravetz@oracle.com> <20220824175757.20590-7-mike.kravetz@oracle.com> <47cc90bf-d616-5004-555d-b3d7e9b09bd1@huawei.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: MW4PR04CA0143.namprd04.prod.outlook.com (2603:10b6:303:84::28) To BY5PR10MB4196.namprd10.prod.outlook.com (2603:10b6:a03:20d::23) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BY5PR10MB4196:EE_|BY5PR10MB4273:EE_ X-MS-Office365-Filtering-Correlation-Id: 29361839-b512-4f6f-232a-08da9112a582 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:(13230016)(7916004)(366004)(346002)(376002)(396003)(39860400002)(136003)(54906003)(6916009)(478600001)(6486002)(2906002)(86362001)(83380400001)(5660300002)(44832011)(8676002)(26005)(186003)(66946007)(8936002)(66556008)(66476007)(4326008)(6666004)(6512007)(9686003)(53546011)(316002)(7416002)(41300700001)(33716001)(38100700002)(6506007)(67856001);DIR:OUT;SFP:1101; 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bh=mYbwBdPYvYK0OAyjjbnbH/jMWa+Abj0KOx7arTY+XFI=; b=LnxHgn8ihZEddTVFDnsU/evyZs/6dUnkNg2sqvRGYfb0WfrCyn70HfkI790/XzaFnWgUfJ jiwtUkOpfW8v50PP6KqV5u9g25ISenDjyb5YQheRd0bkaFJzMaVzolGZ/sWMX+d6/+Uklf KYCTMW55J7YMxAanZYrId5ZCCtXtPoI= X-Rspam-User: X-Rspamd-Queue-Id: D323818006E Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=oracle.com header.s=corp-2022-7-12 header.b=UgCJ5MXi; dkim=pass header.d=oracle.onmicrosoft.com header.s=selector2-oracle-onmicrosoft-com header.b=klPC6RNV; spf=pass (imf06.hostedemail.com: domain of mike.kravetz@oracle.com designates 205.220.165.32 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: f6rdwadrn55zd184nnd567gqkh8bc4kq X-Rspamd-Server: rspam03 X-HE-Tag: 1662583865-645843 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 08/29/22 15:24, Mike Kravetz wrote: > On 08/27/22 17:30, Miaohe Lin wrote: > > On 2022/8/25 1:57, Mike Kravetz wrote: > > > Allocate a rw semaphore and hang off vm_private_data for > > > synchronization use by vmas that could be involved in pmd sharing. Only > > > add infrastructure for the new lock here. Actual use will be added in > > > subsequent patch. > > > > > > Signed-off-by: Mike Kravetz > > > > > > > > > +static void hugetlb_vma_lock_free(struct vm_area_struct *vma) > > > +{ > > > + /* > > > + * Only present in sharable vmas. See comment in > > > + * __unmap_hugepage_range_final about the neeed to check both > > > > s/neeed/need/ > > > > > + * VM_SHARED and VM_MAYSHARE in free path > > > > I think there might be some wrong checks around this patch. As above comment said, we > > need to check both flags, so we should do something like below instead? > > > > if (!(vma->vm_flags & (VM_MAYSHARE | VM_SHARED) == (VM_MAYSHARE | VM_SHARED))) > > > > > + */ > > Thanks. I will update. > > > > + if (!vma || !(vma->vm_flags & (VM_MAYSHARE | VM_SHARED))) > > > + return; I think you misunderstood the comment which I admit was not very clear. And, I misunderstood your suggestion. I believe the code is correct as it. Here is the proposed update comment/code: /* * Only present in sharable vmas. See comment in * __unmap_hugepage_range_final about how VM_SHARED could * be set without VM_MAYSHARE. As a result, we need to * check if either is set in the free path. */ if (!vma || !(vma->vm_flags & (VM_MAYSHARE | VM_SHARED))) return; Hopefully, that makes more sense. -- Mike Kravetz