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 A846EC28D13 for ; Thu, 25 Aug 2022 07:58:42 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 32E8B940009; Thu, 25 Aug 2022 03:58:42 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2DEF4940007; Thu, 25 Aug 2022 03:58:42 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 17FD6940009; Thu, 25 Aug 2022 03:58:42 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 0B31D940007 for ; Thu, 25 Aug 2022 03:58:42 -0400 (EDT) Received: from smtpin01.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id D68DA1603A4 for ; Thu, 25 Aug 2022 07:58:41 +0000 (UTC) X-FDA: 79837363242.01.144576B Received: from out199-4.us.a.mail.aliyun.com (out199-4.us.a.mail.aliyun.com [47.90.199.4]) by imf06.hostedemail.com (Postfix) with ESMTP id E2922180002 for ; Thu, 25 Aug 2022 07:58:39 +0000 (UTC) X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R621e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018045176;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=6;SR=0;TI=SMTPD_---0VNCWwDS_1661414314; Received: from 30.97.48.44(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0VNCWwDS_1661414314) by smtp.aliyun-inc.com; Thu, 25 Aug 2022 15:58:35 +0800 Message-ID: <3c381602-26ea-883c-859a-4007cb7cb289@linux.alibaba.com> Date: Thu, 25 Aug 2022 15:58:45 +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 v2 1/5] mm/hugetlb: fix races when looking up a CONT-PTE size hugetlb page To: David Hildenbrand , Mike Kravetz Cc: akpm@linux-foundation.org, songmuchun@bytedance.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <0e5d92da043d147a867f634b17acbcc97a7f0e64.1661240170.git.baolin.wang@linux.alibaba.com> <4c24b891-04ce-2608-79d2-a75dc236533f@redhat.com> <376d2e0a-d28a-984b-903c-1f6451b04a15@linux.alibaba.com> <7d4e7f47-30a5-3cc6-dc9f-aa89120847d8@redhat.com> <64669c0a-4a6e-f034-a15b-c4a8deea9e5d@linux.alibaba.com> <7ee73879-e402-9175-eae8-41471d80d59e@redhat.com> <50703dda-bbee-7484-97ff-87d6ea75bf80@redhat.com> From: Baolin Wang In-Reply-To: <50703dda-bbee-7484-97ff-87d6ea75bf80@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit ARC-Authentication-Results: i=1; imf06.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=alibaba.com; spf=pass (imf06.hostedemail.com: domain of baolin.wang@linux.alibaba.com designates 47.90.199.4 as permitted sender) smtp.mailfrom=baolin.wang@linux.alibaba.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1661414321; a=rsa-sha256; cv=none; b=gHKo4sHFM2KfjJTogN1g6Nq6oqHV1oaF6UPL/9mnaoHpA2E4ZzGnYehQ+f3p0nefmRCvgU HjScKnnrgohVF1h3SBvPIDjAVMrmMXXeatbTQf8gqpmgV0lu7Z+S6vfpuXZI5b/BQJiFpL tTbhsVxRPieV68bCxIjO+yKej74s0A4= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1661414321; 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=rTCDHhOdVzYFTlhsirgcDjPueJaTwjffwTVyx/XlaAk=; b=zEG2fLr+QMnwomtYL/zOJWgXpMdUP4aFOGR0H+lI7GHkYCwRmPYGlrWLHk+Oz5spWFkQeN DrUpusEtPrVTZK/3lQzBu4Yv9ySo8Cc5dpMCG6k0oTYjDkOJpsaUfd+D5xjRpEjSApN3UK iXN6MD5sYKZ+V16FAXyu/d0ROmM8CBg= X-Rspam-User: X-Rspamd-Queue-Id: E2922180002 X-Stat-Signature: tcxrzabaheaxurt4c76yqo74sfe1jdb6 Authentication-Results: imf06.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=alibaba.com; spf=pass (imf06.hostedemail.com: domain of baolin.wang@linux.alibaba.com designates 47.90.199.4 as permitted sender) smtp.mailfrom=baolin.wang@linux.alibaba.com X-Rspamd-Server: rspam01 X-HE-Tag: 1661414319-935424 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 8/25/2022 3:10 PM, David Hildenbrand wrote: > >>> + /* >>> + * try_grab_page() should always succeed here, because we hold >>> + * the ptl lock and have verified pte_present(). >>> + */ >>> + if (WARN_ON_ONCE(!try_grab_page(page, flags))) { >>> + page = NULL; >>> + goto out; >>> + } >>> + } else { >> >> Should add FOLL_MIGRATION validation before waiting a migration entry. > > We really only need FOLL_MIGRATION for KSM. As hugetlb pages cannot be > KSM pages, we don't need this. > > Actually, I do have patches in the works that rip out FOLL_MIGRATION > completely by adjusting KSM code. > > So let's try to not add dead code (although it would make sense for > feature completeness as is -- but then, FOLL_MIGRATION really needs to go). Make sense. Thanks for your explanation.