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 A6872C19F2C for ; Thu, 4 Aug 2022 07:44:53 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 233AB8E0003; Thu, 4 Aug 2022 03:44:53 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 1E3098E0001; Thu, 4 Aug 2022 03:44:53 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0FA168E0003; Thu, 4 Aug 2022 03:44:53 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 016CA8E0001 for ; Thu, 4 Aug 2022 03:44:52 -0400 (EDT) Received: from smtpin22.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id B9603A033B for ; Thu, 4 Aug 2022 07:44:52 +0000 (UTC) X-FDA: 79761123624.22.F795F8C Received: from out0.migadu.com (out0.migadu.com [94.23.1.103]) by imf13.hostedemail.com (Postfix) with ESMTP id 31A1720008 for ; Thu, 4 Aug 2022 07:44:52 +0000 (UTC) Date: Thu, 4 Aug 2022 16:44:44 +0900 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1659599090; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=7zrMafA/86PiYIeMqh2hEYMbncktkYrbFlWU8+oQQI0=; b=FQyYAptT4/w13rMekB6dEv9UZSjfysjISClpqkD/C5OxGMYgOZDlBo2jel9xya/A9+iScI ckQAb7wocLF4PvBNSxy1yXonhk/rh+2D4AYgWNXEseRMs/Z6K916WmOTB4FwB555xvNizg 3+fXCtUV6/oNO2h27/tWCuHnX8mf9Ps= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Naoya Horiguchi To: Miaohe Lin Cc: Muchun Song , Linux-MM , linux-kernel , Andrew Morton , Mike Kravetz Subject: Re: [bug report] mm, hwpoison: memory_failure races with alloc_fresh_huge_page/free_huge_page Message-ID: <20220804074444.GB2551573@ik1-406-35019.vs.sakura.ne.jp> References: <3c542543-0965-ef60-4627-1a4116077a5b@huawei.com> <20220804074025.GA2551573@ik1-406-35019.vs.sakura.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20220804074025.GA2551573@ik1-406-35019.vs.sakura.ne.jp> X-Migadu-Flow: FLOW_OUT X-Migadu-Auth-User: linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1659599092; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=7zrMafA/86PiYIeMqh2hEYMbncktkYrbFlWU8+oQQI0=; b=vuTV8Py6y4nkPkU3SzmuDSDV3uUThqF4r+79IxDzmqSQKFV9u1oblEOgFu2wrmIjA4hnfs DHsXAIkzDvgJpMpV51HO+FbUwBPMnr8gV/78/NgpLaRRZB+29XIDyWPthNXkJU4kfgF78P L7ebRjcQvFUE9AMczi5q+pkH6t8zZgA= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=FQyYAptT; spf=pass (imf13.hostedemail.com: domain of naoya.horiguchi@linux.dev designates 94.23.1.103 as permitted sender) smtp.mailfrom=naoya.horiguchi@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1659599092; a=rsa-sha256; cv=none; b=zWvmtUWLztUCoL2tZ85EP5tTd2CXA8YMemebzztMqnxuBz54wtnHTS4G4cyqRmYF1LGGdN p9o3Swk1tlzDDBFygpn4XLR7ADeGjMPlk69IMIw8WQ4HXBBBw45Tom0PiJvPahwwPPOrEH pv3gv8IovoHWIGy7+XT/wB3o+OXAx0o= X-Rspam-User: Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=FQyYAptT; spf=pass (imf13.hostedemail.com: domain of naoya.horiguchi@linux.dev designates 94.23.1.103 as permitted sender) smtp.mailfrom=naoya.horiguchi@linux.dev; dmarc=pass (policy=none) header.from=linux.dev X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 31A1720008 X-Stat-Signature: skswezns8bae635qgnntfzb5o1anpr14 X-HE-Tag: 1659599092-410018 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 Thu, Aug 04, 2022 at 04:40:25PM +0900, Naoya Horiguchi wrote: > On Tue, Aug 02, 2022 at 02:27:36PM +0800, Miaohe Lin wrote: > > On 2022/8/2 12:07, Muchun Song wrote: > > > On Tue, Aug 02, 2022 at 10:00:50AM +0800, Miaohe Lin wrote: > > >> Hi all: > > >> When I investigate the mm/memory-failure.c code again, I found there's a possible race window > > >> between memory_failure and alloc_fresh_huge_page/free_huge_page. Thank about the below scene: > > >> > > >> CPU 1 CPU 2 > > >> alloc_fresh_huge_page -- page refcnt > 0 memory_failure > > >> prep_new_huge_page get_huge_page_for_hwpoison > > >> !PageHeadHuge -- so 2(not a hugepage) is returned > > >> hugetlb_vmemmap_optimize -- subpages is read-only > > >> set_compound_page_dtor -- PageHuge is true now, but too late!!! > > >> TestSetPageHWPoison(p) > > >> -- We might write to read-only subpages here!!! > > >> > > >> Another similar scene: > > >> > > >> CPU 1 CPU 2 > > >> free_huge_page -- page refcnt == 0 and not PageHuge memory_failure > > >> get_huge_page_for_hwpoison > > >> !PageHeadHuge -- so 2(not a hugepage) is returned > > >> TestSetPageHWPoison(p) > > >> -- We might write to read-only subpages here!!! > > >> hugetlb_vmemmap_restore -- subpages can be written to now, but too late!!! > > >> > > > > > > I agree this race is possible, I have proposed this race in thread [1]. > > Thank you for reminding this, and I agree that we need some solution. > > > > > Oh, I remember I see the race proposed in [1] but I did not look into that carefully at that time. Sorry. > > > > > But I didn't think more how to solve it. > > I hope this thread can find a good solution. :) > > Both of the races show that __get_huge_page_for_hwpoison() fails to > capture the case of generic compound page during turning into hugetlb, I noticed my wrong description just after sending this out. The second race is about generic compound page turning into "buddy", sorry. - Naoya Horiguchi > What makes things complicated is that no one knows to which state > such a compound page finally turns into. So I think that if the page > to be handled is an unknown compound page, we need to wait until it > becomes some known page state to avoid misjudging. > > If we need a quick small fix, we may replace the check "!PageHeadHuge()" > in __get_huge_page_for_hwpoison() with "!PageCompound()", and add another > retry path in get_huge_page_for_hwpoison() for non-hugetlb compound pages. > > Thanks, > Naoya Horiguchi