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 04C5AC433EF for ; Tue, 12 Apr 2022 02:48:01 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 46B1B6B0071; Mon, 11 Apr 2022 22:48:01 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 41A576B0073; Mon, 11 Apr 2022 22:48:01 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2E2346B0074; Mon, 11 Apr 2022 22:48:01 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0252.hostedemail.com [216.40.44.252]) by kanga.kvack.org (Postfix) with ESMTP id 1F3C56B0071 for ; Mon, 11 Apr 2022 22:48:01 -0400 (EDT) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id B217CA5BD4 for ; Tue, 12 Apr 2022 02:48:00 +0000 (UTC) X-FDA: 79346692320.27.6EB003F Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by imf26.hostedemail.com (Postfix) with ESMTP id 336F514000A for ; Tue, 12 Apr 2022 02:47:59 +0000 (UTC) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.57]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4KcqrT1ZZ7z1HBn2; Tue, 12 Apr 2022 10:47:21 +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; Tue, 12 Apr 2022 10:47:53 +0800 Subject: Re: [PATCH 3/3] mm/memory-failure.c: dissolve truncated hugetlb page To: =?UTF-8?B?SE9SSUdVQ0hJIE5BT1lBKOWggOWPoyDnm7TkuZ8p?= CC: "akpm@linux-foundation.org" , "shy828301@gmail.com" , "mike.kravetz@oracle.com" , "david@redhat.com" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" References: <20220407130352.15618-1-linmiaohe@huawei.com> <20220407130352.15618-4-linmiaohe@huawei.com> <20220411131344.GA3188122@hori.linux.bs1.fc.nec.co.jp> From: Miaohe Lin Message-ID: Date: Tue, 12 Apr 2022 10:47:53 +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: <20220411131344.GA3188122@hori.linux.bs1.fc.nec.co.jp> Content-Type: text/plain; charset="utf-8" Content-Language: en-US X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected Authentication-Results: imf26.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf26.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.255 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com X-Stat-Signature: hdr6suzwdm1s8jbxk5rwkmx183so6qdg X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 336F514000A X-HE-Tag: 1649731679-658639 Content-Transfer-Encoding: quoted-printable 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 2022/4/11 21:13, HORIGUCHI NAOYA(=E5=A0=80=E5=8F=A3 =E7=9B=B4=E4=B9=9F= ) wrote: > Hi Miaohe, >=20 > On Thu, Apr 07, 2022 at 09:03:52PM +0800, Miaohe Lin wrote: >> If me_huge_page meets a truncated huge page, hpage won't be dissolved >=20 > I might not understand correctly what "truncated huge page" means. If = it > means the page passed to me_huge_page() and truncate_error_page() is ca= lled > on it, the else branch you're trying to update is not chosen, so maybe = it > sounds irrelevant to me? Could you elaborate it or share the procedure= to > reproduce the case you care about? Sorry for making confusing. What 'truncated hugetlb page' means is that a= hugepage is truncated but still on the way to free. So HPageMigratable is still set a= nd we might come across it here. Does this make sense for you? >=20 >> even if we hold the last refcnt. It's because the truncated huge page >> has NULL page_mapping while it's not anonymous page too. Thus we lose >> the last chance to dissolve it into buddy to save healthy subpages. >> Remove PageAnon check to handle these huge pages too. >> >> Signed-off-by: Miaohe Lin >> --- >> mm/memory-failure.c | 3 +-- >> 1 file changed, 1 insertion(+), 2 deletions(-) >> >> diff --git a/mm/memory-failure.c b/mm/memory-failure.c >> index bd563f47630c..3f054dbb169d 100644 >> --- a/mm/memory-failure.c >> +++ b/mm/memory-failure.c >> @@ -1046,8 +1046,7 @@ static int me_huge_page(struct page_state *ps, s= truct page *p) >> * hugepage, so we can free and dissolve it into buddy to >> * save healthy subpages. >> */ >> - if (PageAnon(hpage)) >> - put_page(hpage); >=20 > I think that the reason of this "if (PageAnon(hpage))" is to not remove > hugepages for hugetlbfs files. Unlike anonymous hugepage, it can be > accessed from file after error handling, so we can't simply dissolve it > because otherwise another process reading the hugepage sees zeroed one > without knowing the memory error. In this branch, we have precondition that page_mapping is NULL. So it can= 't be hugepages for hugetlbfs files. It should be anonymous hugepages in most cases. If i= t's not anonymous hugepages too, i.e. (!page_mapping(hpage) && !PageAnon(hpage)), it could = be free hugepages or 'truncated hugetlb page'. But we have already handled the free hugepag= es case, it should be 'truncated hugetlb page' here. Since it's on the way to free, we shoul= d put the refcnt to increase the chance that we can free and dissolve it into buddy to sav= e healthy subpages. Or am I miss something? Thanks! >=20 > Thanks, > Naoya Horiguchi >=20 >> + put_page(hpage); >> if (__page_handle_poison(p)) { >> page_ref_inc(p); >> res =3D MF_RECOVERED; >> --=20 >> 2.23.0