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 2829BC38145 for ; Thu, 8 Sep 2022 02:04:28 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9C6E16B0072; Wed, 7 Sep 2022 22:04:27 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 975C26B0073; Wed, 7 Sep 2022 22:04:27 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 864718D0001; Wed, 7 Sep 2022 22:04:27 -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 7A5576B0072 for ; Wed, 7 Sep 2022 22:04:27 -0400 (EDT) Received: from smtpin05.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 3E3CD160B1E for ; Thu, 8 Sep 2022 02:04:27 +0000 (UTC) X-FDA: 79887273774.05.9E8D57C Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) by imf12.hostedemail.com (Postfix) with ESMTP id 481AE4008C for ; Thu, 8 Sep 2022 02:04:26 +0000 (UTC) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.55]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4MNMnv02qvzHnbw; Thu, 8 Sep 2022 10:02:27 +0800 (CST) Received: from [10.174.177.76] (10.174.177.76) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Thu, 8 Sep 2022 10:04:21 +0800 Subject: Re: [PATCH 6/8] hugetlb: add vma based lock for pmd sharing To: Mike Kravetz CC: Muchun Song , David Hildenbrand , Michal Hocko , Peter Xu , Naoya Horiguchi , "Aneesh Kumar K . V" , Andrea Arcangeli , "Kirill A . Shutemov" , Davidlohr Bueso , Prakash Sangappa , James Houghton , Mina Almasry , Pasha Tatashin , Axel Rasmussen , Ray Fucillo , Andrew Morton , , References: <20220824175757.20590-1-mike.kravetz@oracle.com> <20220824175757.20590-7-mike.kravetz@oracle.com> <47cc90bf-d616-5004-555d-b3d7e9b09bd1@huawei.com> From: Miaohe Lin Message-ID: <8a4b3ff7-a25f-d1c2-0300-c28c8577eae7@huawei.com> Date: Thu, 8 Sep 2022 10:04:21 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected ARC-Authentication-Results: i=1; imf12.hostedemail.com; dkim=none; spf=pass (imf12.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.189 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com; dmarc=pass (policy=quarantine) header.from=huawei.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1662602667; a=rsa-sha256; cv=none; b=v7+hAeg9qhk1wGRolT1KrSUmvlS6nLZZC7RpivBaqr8+DN9jzR2RdWkEus1OJvv+WXOV9r rYJ8Ini7j93Ajt97HcS99yv1X8CLTF+2gBl5GSBSxgf48DOFgYR4QTWwsYgt8IseFvyK+D kXZlFQv7kzRn/QY1eD3feuxP9fgckYI= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1662602667; 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:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=YShet/2VO7AfB22fxoSQ90JQjCmCBnRV+0R1oT3D7kU=; b=tkCi2Che6LFQ7rd/2yEtB/Q54N6xv/ufQMdPyNfaMaPiZOlXzENayswn6BdIyq0lDuibt4 AJkqrydrwCLE9xRefyPUtvr5Qf36v0M0ZgL1lPMHfcQo4JdMcQdMecfmiQuUnM90GYEia5 yOfFMjZgUCwjUclYksuNXPynWvFJO/E= X-Rspamd-Queue-Id: 481AE4008C X-Rspam-User: Authentication-Results: imf12.hostedemail.com; dkim=none; spf=pass (imf12.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.189 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com; dmarc=pass (policy=quarantine) header.from=huawei.com X-Rspamd-Server: rspam01 X-Stat-Signature: p74d9bwmwoard44tosmscog8fnohfu64 X-HE-Tag: 1662602666-551110 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 2022/9/8 4:50, Mike Kravetz wrote: > 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. Somewhat confusing. Thanks for clarifying, Mike. Thanks, Miaohe Lin