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 EE0C5C00140 for ; Sun, 21 Aug 2022 05:54:31 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 53F0F8D0002; Sun, 21 Aug 2022 01:54:31 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4EEAC8D0001; Sun, 21 Aug 2022 01:54:31 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3DDBD8D0002; Sun, 21 Aug 2022 01:54:31 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 2E7918D0001 for ; Sun, 21 Aug 2022 01:54:31 -0400 (EDT) Received: from smtpin26.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 02EAAC01A3 for ; Sun, 21 Aug 2022 05:54:30 +0000 (UTC) X-FDA: 79822535142.26.2F3DE38 Received: from out30-56.freemail.mail.aliyun.com (out30-56.freemail.mail.aliyun.com [115.124.30.56]) by imf22.hostedemail.com (Postfix) with ESMTP id E8396C0177 for ; Sun, 21 Aug 2022 05:54:28 +0000 (UTC) X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R981e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018045168;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=5;SR=0;TI=SMTPD_---0VMmZtHX_1661061264; Received: from 30.15.206.157(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0VMmZtHX_1661061264) by smtp.aliyun-inc.com; Sun, 21 Aug 2022 13:54:25 +0800 Message-ID: <8b4fc8cc-23c0-8629-1225-eefcbab1f039@linux.alibaba.com> Date: Sun, 21 Aug 2022 13:54:37 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.12.0 Subject: Re: [PATCH 0/3] Fix some issues when looking up hugetlb page To: Mike Kravetz Cc: akpm@linux-foundation.org, songmuchun@bytedance.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: From: Baolin Wang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1661061270; a=rsa-sha256; cv=none; b=T+YAS5uFGcIKlDVcBHtmRmlduDGU7PQwujmSVRrc6LgzrS6NWeLQlk8oLbSWxTXCbmCSmT UR4ljza3MG9qvhCL/8L+H+/CpvAVWnTNzt/Q+HsMWHGwocW3GepdgLgZVFmEBRZ6Htk/yv eo/GJ38beTJcBuLKIq8lB22waMAcDfY= ARC-Authentication-Results: i=1; imf22.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=alibaba.com; spf=pass (imf22.hostedemail.com: domain of baolin.wang@linux.alibaba.com designates 115.124.30.56 as permitted sender) smtp.mailfrom=baolin.wang@linux.alibaba.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1661061270; 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=oHusiSg5bOD9jbOMX+rTmC2C0WgoJ7qxT+MOGPSZwwA=; b=yZo8/MjpFPHlOJBt9u4xGoUMZBjnLyPttI6HtfMh2ATP/nCG3Lpl63OBVetzFbXbv+QL9f Yf9+I8H/6iV04aMFfl3gwEwQnBqqnqReYWfCchmctq6iLpN0SEnHAuO8cRI85eQx7NhIB7 UiATeLuAgq/E9uKV0ihcaZiE1F318iE= X-Rspamd-Queue-Id: E8396C0177 X-Stat-Signature: magg8d5md656r1it53fwbcrmhw8b16oq Authentication-Results: imf22.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=alibaba.com; spf=pass (imf22.hostedemail.com: domain of baolin.wang@linux.alibaba.com designates 115.124.30.56 as permitted sender) smtp.mailfrom=baolin.wang@linux.alibaba.com X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1661061268-962065 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 8/20/2022 8:08 AM, Mike Kravetz wrote: > On 08/19/22 18:12, Baolin Wang wrote: >> Hi, >> >> On ARM64 architecture, it can support CONT-PTE/PMD size hugetlb. When >> looking up hugetlb page by follow_page(), we will hold the incorrect >> pte/pmd lock for the CONT-PTE/PMD size hugetlb page, which will make >> the pte/pmd entry unstable even under the lock and cause some potential >> race issues. So considering the CONT-PTE/PMD size hugetlb, this patch set >> changes to use the correct function to get the correct pte/pmd entry lock >> to make the pte/pmd entry stable. > > Thank you for looking at this. > > I often get confused by arm64 CONT-PTE/PMD layout, so my understanding may be > wrong. Can we use the PMD page lock for locking both CONT-PTE and CONT-PMD > entries? Again, I may be confused by the CONT-* page table layout, but it > seems these would all be referenced via that same PMD page of the page table. > Or, perhaps CONT-PMD can span multiple PMD pages? Good point. CONT-PMD can not span multiple PMD pages, so I think CONT-PMD can use PMD pagetable page lock, but CONT-PTE also can not span multiple PTE pagetable page lock, so I think CONT-PTE can use the PTE pagetable page lock to get a fine grained lock. I will add CONT-PTE and CONT-PMD case in huge_pte_lockptr() in next version. Thanks for your comment. > If we can use PMD page for locking, this would be much finer grain that > lock in the mm.