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 172CFC54EE9 for ; Fri, 9 Sep 2022 00:27:55 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A85358D0005; Thu, 8 Sep 2022 20:27:54 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A0D678D0001; Thu, 8 Sep 2022 20:27:54 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8871B8D0005; Thu, 8 Sep 2022 20:27:54 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 734C68D0001 for ; Thu, 8 Sep 2022 20:27:54 -0400 (EDT) Received: from smtpin06.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 503C31A02FC for ; Fri, 9 Sep 2022 00:27:54 +0000 (UTC) X-FDA: 79890659268.06.384C44F Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by imf05.hostedemail.com (Postfix) with ESMTP id 4D7B410008E for ; Fri, 9 Sep 2022 00:27:53 +0000 (UTC) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.57]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4MNxZ42VvpzmVFb; Fri, 9 Sep 2022 08:24:12 +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; Fri, 9 Sep 2022 08:27:49 +0800 Subject: Re: [PATCH] mm/huge_memory: use pfn_to_online_page() in split_huge_pages_all() To: Michal Hocko CC: =?UTF-8?B?SE9SSUdVQ0hJIE5BT1lBKOWggOWPoyDnm7TkuZ8p?= , Naoya Horiguchi , David Hildenbrand , "linux-mm@kvack.org" , Andrew Morton , Muchun Song , Matthew Wilcox , Yang Shi References: <20220907100855.GA2894785@ik1-406-35019.vs.sakura.ne.jp> <1481ce19-0a64-d1dc-4d89-4db71d6f7eb3@redhat.com> <20220907121157.GA2954283@ik1-406-35019.vs.sakura.ne.jp> <9cb0b01e-c80d-667c-47f1-ad30e329784b@huawei.com> <20220908030652.GA1492282@hori.linux.bs1.fc.nec.co.jp> From: Miaohe Lin Message-ID: <2d0792c0-88e1-710c-c8bd-c126cc375e88@huawei.com> Date: Fri, 9 Sep 2022 08:27:48 +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: 8bit X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1662683274; a=rsa-sha256; cv=none; b=oGuA2+bs89SjCBDVAN7j3k1iFbc3vDGN7dQWOsml40tKv4mdrRx3HAN4CIuq9CwKaq2cqs p3mYKGyd0aXxgzesL8/SbQoH3fS02cm7+kfH6j6TlGBvw2LiZPdhlVft8t6KZy3fr1pr3C eqJn/JgM8lHPzCb3pxnO0j5a9e9TLr4= ARC-Authentication-Results: i=1; imf05.hostedemail.com; dkim=none; spf=pass (imf05.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.188 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com; dmarc=pass (policy=quarantine) header.from=huawei.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1662683274; 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=kqVHkY/nbXtqGY1C7pLQYr8xdsAUoZh0yLh4wPex3ik=; b=YdOkJ2bdPQGR1IoCown+zIFf4FAh9Gya7u2wRJrfL6+nKy/f8zR6SXdDuHzZ51b/Vl1MdH uSOQ8TpbonzBNx/Uj2COQR/rtpG9536mVbiEKFIgM2gZV5HQmVm/O3TQR7TAMkkt2G6gMY tu+DHgJ9i2wGQXyATO3Z9uR0Bvgqhus= X-Rspamd-Server: rspam03 X-Rspam-User: X-Stat-Signature: nzenomyubndx9qwhxrnssen8fishw9gt X-Rspamd-Queue-Id: 4D7B410008E Authentication-Results: imf05.hostedemail.com; dkim=none; spf=pass (imf05.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.188 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com; dmarc=pass (policy=quarantine) header.from=huawei.com X-HE-Tag: 1662683273-925464 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 15:07, Michal Hocko wrote: > On Thu 08-09-22 11:25:54, Miaohe Lin wrote: >> On 2022/9/8 11:06, HORIGUCHI NAOYA(堀口 直也) wrote: >>> On Thu, Sep 08, 2022 at 10:19:03AM +0800, Miaohe Lin wrote: >>>> On 2022/9/7 20:11, Naoya Horiguchi wrote: >>> ... >>>>> >From 8a5c284df732943065d23838090d15c94cd10395 Mon Sep 17 00:00:00 2001 >>>>> From: Naoya Horiguchi >>>>> Date: Wed, 7 Sep 2022 20:58:44 +0900 >>>>> Subject: [PATCH] mm/huge_memory: use pfn_to_online_page() in >>>>> split_huge_pages_all() >>>>> >>>>> NULL pointer dereference is triggered when calling thp split via debugfs >>>>> on the system with offlined memory blocks. With debug option enabled, >>>>> the following kernel messages are printed out: >>>>> >>>>> page:00000000467f4890 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x121c000 >>>>> flags: 0x17fffc00000000(node=0|zone=2|lastcpupid=0x1ffff) >>>>> raw: 0017fffc00000000 0000000000000000 dead000000000122 0000000000000000 >>>>> raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000 >>>>> page dumped because: unmovable page >>>>> page:000000007d7ab72e is uninitialized and poisoned >>>>> page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p)) >>>>> ------------[ cut here ]------------ >>>>> kernel BUG at include/linux/mm.h:1248! >>>>> invalid opcode: 0000 [#1] PREEMPT SMP PTI >>>>> CPU: 16 PID: 20964 Comm: bash Tainted: G I 6.0.0-rc3-foll-numa+ #41 >>>>> ... >>>>> RIP: 0010:split_huge_pages_write+0xcf4/0xe30 >>>>> >>>>> This shows that page_to_nid() in page_zone() is unexpectedly called for an >>>>> offlined memmap. >>>>> >>>>> Use pfn_to_online_page() to get struct page in PFN walker. >>>> >>>> With changes proposed by David, this patch looks good to me. >>>> >>>> Reviewed-by: Miaohe Lin >>> >>> Thank you. >>> >>>> >>>> BTW: IMHO, there might be many similar code places need to take care of memory hotremove where >>>> *pfn is operated directly* while it's not protected against memory hotremove. >>> >>> I had the similar concern, but there seems many place doing PFN walk, >>> so checking them one-by-one that offlined memory can be walked over >>> requires much effort. >> >> Yes, that will be a heavy work. We could fix them one by one if they ever occur. ;) > > Most of those whic are directly triggerable should be taken care of. It > would be still good to go through `git grep -w pfn_to_page' and evaluate > all callers. Still more than 400 callsites so not a trivial task. Agree. Even if pfn_to_online_page() is used, it might still races with the memory hotremove if there's no way to guard against it, e.g. holding an extra page refcnt. So code audit should also apply to pfn_to_online_page(). Thanks, Miaohe Lin