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 X-Spam-Level: X-Spam-Status: No, score=-5.5 required=3.0 tests=INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B25A0ECE587 for ; Mon, 14 Oct 2019 08:39:18 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 7C16120650 for ; Mon, 14 Oct 2019 08:39:18 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7C16120650 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 283D08E0005; Mon, 14 Oct 2019 04:39:18 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2338F8E0001; Mon, 14 Oct 2019 04:39:18 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1232A8E0005; Mon, 14 Oct 2019 04:39:18 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0247.hostedemail.com [216.40.44.247]) by kanga.kvack.org (Postfix) with ESMTP id E0F288E0001 for ; Mon, 14 Oct 2019 04:39:17 -0400 (EDT) Received: from smtpin16.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with SMTP id 761EC181AEF2A for ; Mon, 14 Oct 2019 08:39:17 +0000 (UTC) X-FDA: 76041740754.16.screw87_33f3f033ac55d X-HE-Tag: screw87_33f3f033ac55d X-Filterd-Recvd-Size: 3625 Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) by imf04.hostedemail.com (Postfix) with ESMTP for ; Mon, 14 Oct 2019 08:39:16 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id A2DABB885; Mon, 14 Oct 2019 08:39:15 +0000 (UTC) Date: Mon, 14 Oct 2019 10:39:14 +0200 From: Michal Hocko To: Qian Cai Cc: Naoya Horiguchi , linux-kernel@vger.kernel.org, linux-mm@kvack.org, David Hildenbrand , Mike Kravetz Subject: Re: memory offline infinite loop after soft offline Message-ID: <20191014083914.GA317@dhcp22.suse.cz> References: <1570829564.5937.36.camel@lca.pw> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <1570829564.5937.36.camel@lca.pw> User-Agent: Mutt/1.10.1 (2018-07-13) 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 Fri 11-10-19 17:32:44, Qian Cai wrote: > # /opt/ltp/runtest/bin/move_pages12 > move_pages12.c:263: INFO: Free RAM 258988928 kB > move_pages12.c:281: INFO: Increasing 2048kB hugepages pool on node 0 to= 4 > move_pages12.c:291: INFO: Increasing 2048kB hugepages pool on node 8 to= 4 > move_pages12.c:207: INFO: Allocating and freeing 4 hugepages on node 0 > move_pages12.c:207: INFO: Allocating and freeing 4 hugepages on node 8 > move_pages12.c:197: PASS: Bug not reproduced > move_pages12.c:197: PASS: Bug not reproduced >=20 > for mem in $(ls -d /sys/devices/system/memory/memory*); do > =A0=A0=A0=A0=A0=A0=A0=A0echo offline > $mem/state > =A0=A0=A0=A0=A0=A0=A0=A0echo online > $mem/state > done >=20 > That LTP move_pages12 test will first madvise(MADV_SOFT_OFFLINE) for a = range. > Then, one of "echo offline" will trigger an infinite loop in __offline_= pages() > here, >=20 > /* check again */ > ret =3D walk_system_ram_range(start_pfn, end_pfn - start_pfn, > =A0=A0=A0=A0NULL, check_pages_isolated_cb); > } while (ret); >=20 > because check_pages_isolated_cb() always return -EBUSY from > test_pages_isolated(), >=20 >=20 > pfn =3D __test_page_isolated_in_pageblock(start_pfn, end_pfn, > skip_hwpoisoned_pages); > ... > return pfn < end_pfn ? -EBUSY : 0; >=20 > The root cause is in __test_page_isolated_in_pageblock() where "pfn" is= always > less than "end_pfn" because the associated page is not a PageBuddy. >=20 > while (pfn < end_pfn) { > ... > else > break; >=20 > return pfn; Hmm, this is interesting. I would expect that this would hit the previous branch if (skip_hwpoisoned_pages && PageHWPoison(page)) and skip over hwpoisoned page. But I cannot seem to find that we would mark all tail pages HWPoison as well and so any tail page seem to confuse __test_page_isolated_in_pageblock. Oscar is rewriting the hwpoison implementation but I am not sure how/whether he is handling this case differently. Naoya, shouldn't we do the following at least? --- diff --git a/mm/page_isolation.c b/mm/page_isolation.c index 89c19c0feadb..5fb3fee16fde 100644 --- a/mm/page_isolation.c +++ b/mm/page_isolation.c @@ -274,7 +274,7 @@ __test_page_isolated_in_pageblock(unsigned long pfn, = unsigned long end_pfn, * simple way to verify that as VM_BUG_ON(), though. */ pfn +=3D 1 << page_order(page); - else if (skip_hwpoisoned_pages && PageHWPoison(page)) + else if (skip_hwpoisoned_pages && PageHWPoison(compound_head(page))) /* A HWPoisoned page cannot be also PageBuddy */ pfn++; else --=20 Michal Hocko SUSE Labs