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 DA9D4C433F5 for ; Tue, 15 Mar 2022 18:20:06 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 281C78D0002; Tue, 15 Mar 2022 14:20:06 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2097E8D0001; Tue, 15 Mar 2022 14:20:06 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0AAB78D0002; Tue, 15 Mar 2022 14:20:06 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0166.hostedemail.com [216.40.44.166]) by kanga.kvack.org (Postfix) with ESMTP id E93898D0001 for ; Tue, 15 Mar 2022 14:20:05 -0400 (EDT) Received: from smtpin25.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 93B719F858 for ; Tue, 15 Mar 2022 18:20:05 +0000 (UTC) X-FDA: 79247434770.25.BF0E179 Received: from mail-pf1-f169.google.com (mail-pf1-f169.google.com [209.85.210.169]) by imf13.hostedemail.com (Postfix) with ESMTP id 1A2B720003 for ; Tue, 15 Mar 2022 18:20:04 +0000 (UTC) Received: by mail-pf1-f169.google.com with SMTP id d19so283695pfv.7 for ; Tue, 15 Mar 2022 11:20:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=sZqFM1DdTzKMCe7Ik7jL3tVTyC3fc1mknILd/ebsH/s=; b=izMD0CGKS3jC9MlY/JKtkSPhr4TH1HycOYlSrgJ024KfcfBa0iPn9+1hOmAjbcZtnp jcyR7rbtlY7Ssx00HZf2a16nEcBMtDIExvhKhn5S9tzgiHM3R2Uhfs7vUgLb8vmmh8GW o9RBuoaHGRo4CG3QFEs9wpmdMfcPTp8higjj2l1S270WLvV0S2rhR/QfCM1EaBqMEshk 505wMwXBd6jplWh0+3lS9lU5DeIQe9Z+zTZfOjxzzZmJH3bBR9RDfNOlhXVX8+cW6BuD L/JgBVLxYiogZnKqmH/vIWiCYSG9d9Z/McTcMUzuLusHLtWZlQNB2vcGvZwLQVrB+ZPB W8sA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=sZqFM1DdTzKMCe7Ik7jL3tVTyC3fc1mknILd/ebsH/s=; b=lM5o8oe6+jwC6TO1+TdLqYHE/KLIFkHs03O8TPUNFZt/S8k2Uhu/4MNrbI3uoEAsTW anpv0ROaTgpn5eu/Gbsxa424JbSlPzsr+U5/OIn4dseskklFiJlqam2Kg5v9OW9lQFAD pa5KPDtlYZKZnLQr+vY6nUZFHqVgpgqjbI7DVh/hn50/SUfo0Tk3PWlCNpnk6nUk3RpE yRtQ8FBIeldvsGkuqkRYksq0D1yivXxKEtAlPuCLSdnaCGqLt9I1g05Wf7BXruTJ5KJ6 pYmD/qxoJJkTOiYEVkYhz7bjqmTHQXLrmnvLn+wbZBgXfFrDbyczWOOlAkST2ToyWcXT 12EQ== X-Gm-Message-State: AOAM531fPB13AF3uOawCToLwYiakcUHdOzuzteW2S7yAdQoDbOJbz3im X60a3NZFFfZMkN2T1XI1btehf6P3yZgLIucNIfo= X-Google-Smtp-Source: ABdhPJxxVuedUSYl+kFkW9kUsJpAyx04kp6BlSZDwIXYON4pKE+lZFdn+gvYQck89RjyNQ8OUPIoiP5GUiqvxPq52a4= X-Received: by 2002:a63:fd01:0:b0:381:31b7:8bc5 with SMTP id d1-20020a63fd01000000b0038131b78bc5mr11746462pgh.206.1647368404061; Tue, 15 Mar 2022 11:20:04 -0700 (PDT) MIME-Version: 1.0 References: <20220312074613.4798-1-linmiaohe@huawei.com> <20220312074613.4798-2-linmiaohe@huawei.com> <91661cd4-e9be-959f-8b6a-da257a00a879@oracle.com> <9826152a-8a83-76a8-ded8-47d185aac0a8@huawei.com> In-Reply-To: <9826152a-8a83-76a8-ded8-47d185aac0a8@huawei.com> From: Yang Shi Date: Tue, 15 Mar 2022 11:19:52 -0700 Message-ID: Subject: Re: [PATCH v2 1/3] mm/memory-failure.c: fix race with changing page compound again To: Miaohe Lin Cc: Mike Kravetz , naoya.horiguchi@nec.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-edac@vger.kernel.org, akpm@linux-foundation.org, tony.luck@intel.com, bp@alien8.de Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 1A2B720003 Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=izMD0CGK; spf=pass (imf13.hostedemail.com: domain of shy828301@gmail.com designates 209.85.210.169 as permitted sender) smtp.mailfrom=shy828301@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Rspam-User: X-Stat-Signature: nenxubnndagtmpkdahxxsq376114xcqp X-HE-Tag: 1647368404-978111 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000461, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Mar 15, 2022 at 7:19 AM Miaohe Lin wrote: > > On 2022/3/15 2:20, Mike Kravetz wrote: > > On 3/11/22 23:46, Miaohe Lin wrote: > >> There is a race window where we got the compound_head, the hugetlb page > >> could be freed to buddy, or even changed to another compound page just > >> before we try to get hwpoison page. Think about the below race window: > >> CPU 1 CPU 2 > >> memory_failure_hugetlb > >> struct page *head = compound_head(p); > >> hugetlb page might be freed to > >> buddy, or even changed to another > >> compound page. > >> > >> get_hwpoison_page -- page is not what we want now... > >> > >> If this race happens, just bail out. Also MF_MSG_DIFFERENT_PAGE_SIZE is > >> introduced to record this event. > >> > >> Signed-off-by: Miaohe Lin > >> --- > >> include/linux/mm.h | 1 + > >> include/ras/ras_event.h | 1 + > >> mm/memory-failure.c | 12 ++++++++++++ > >> 3 files changed, 14 insertions(+) > >> > >> diff --git a/include/linux/mm.h b/include/linux/mm.h > >> index c9bada4096ac..ef98cff2b253 100644 > >> --- a/include/linux/mm.h > >> +++ b/include/linux/mm.h > >> @@ -3253,6 +3253,7 @@ enum mf_action_page_type { > >> MF_MSG_BUDDY, > >> MF_MSG_DAX, > >> MF_MSG_UNSPLIT_THP, > >> + MF_MSG_DIFFERENT_PAGE_SIZE, > >> MF_MSG_UNKNOWN, > >> }; > >> > >> diff --git a/include/ras/ras_event.h b/include/ras/ras_event.h > >> index d0337a41141c..1e694fd239b9 100644 > >> --- a/include/ras/ras_event.h > >> +++ b/include/ras/ras_event.h > >> @@ -374,6 +374,7 @@ TRACE_EVENT(aer_event, > >> EM ( MF_MSG_BUDDY, "free buddy page" ) \ > >> EM ( MF_MSG_DAX, "dax page" ) \ > >> EM ( MF_MSG_UNSPLIT_THP, "unsplit thp" ) \ > >> + EM ( MF_MSG_DIFFERENT_PAGE_SIZE, "different page size" ) \ > >> EMe ( MF_MSG_UNKNOWN, "unknown page" ) > >> > >> /* > >> diff --git a/mm/memory-failure.c b/mm/memory-failure.c > >> index 5444a8ef4867..dabecd87ad3f 100644 > >> --- a/mm/memory-failure.c > >> +++ b/mm/memory-failure.c > >> @@ -733,6 +733,7 @@ static const char * const action_page_types[] = { > >> [MF_MSG_BUDDY] = "free buddy page", > >> [MF_MSG_DAX] = "dax page", > >> [MF_MSG_UNSPLIT_THP] = "unsplit thp", > >> + [MF_MSG_DIFFERENT_PAGE_SIZE] = "different page size", > >> [MF_MSG_UNKNOWN] = "unknown page", > >> }; > >> > >> @@ -1534,6 +1535,17 @@ static int memory_failure_hugetlb(unsigned long pfn, int flags) > >> } > >> > >> lock_page(head); > >> + > >> + /** > >> + * The page could have changed compound pages due to race window. > >> + * If this happens just bail out. > >> + */ > >> + if (!PageHuge(p) || compound_head(p) != head) { > >> + action_result(pfn, MF_MSG_DIFFERENT_PAGE_SIZE, MF_IGNORED); > >> + res = -EBUSY; > > > > We have discussed this race in other versions of the patch. When we encounter > > the race, we have likely marked poison on the wrong page. Correct? > > > > Many thanks for comment. > I assume that Naoya's patch "mm/hwpoison: set PageHWPoison after taking page lock > in memory_failure_hugetlb()" would set the PageHWPoison after the above check. > So I think the below operation is not needed as PageHWPoison is not set yet. > Does this makes sense for you? I'm wondering if it might be better and helpful for review to squash this patch with Naoya's patch together? It seems we always missed the other part when reviewing the patches. > > Thanks. > > > Instead of printing a "different page size", would it be better to perhaps: > > - Print a message that wrong page may be marked for poison? > > - Clear the poison flag in the "head page" previously set? > > >