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=-5.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 D9A4DECE58D for ; Mon, 14 Oct 2019 08:39:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AE2AD207FF for ; Mon, 14 Oct 2019 08:39:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1571042358; bh=/iRUtYW2DqEiFpeYYYWspGOKICVFzaiC9FJCCvg2pvs=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=enY/TWykKcyJfY+U6WBALJE5e4XbmO6W8LLOUtwRSOwJNt50Hv3EzKg+I6T0SK4Gf BLAQ6EeqBBfZILkC4hBGA6GCUA9kmrqMMgrtlxOwTI33xVVhGJZ1pzHzEGeNwbnvFZ ZFbH+q+XHe24nhDltaGFdVNApW9tMhq43ZPd6IGY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730533AbfJNIjR (ORCPT ); Mon, 14 Oct 2019 04:39:17 -0400 Received: from mx2.suse.de ([195.135.220.15]:38758 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729234AbfJNIjR (ORCPT ); Mon, 14 Oct 2019 04:39:17 -0400 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 Content-Transfer-Encoding: 8bit In-Reply-To: <1570829564.5937.36.camel@lca.pw> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > > for mem in $(ls -d /sys/devices/system/memory/memory*); do >         echo offline > $mem/state >         echo online > $mem/state > done > > 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, > > /* check again */ > ret = walk_system_ram_range(start_pfn, end_pfn - start_pfn, >     NULL, check_pages_isolated_cb); > } while (ret); > > because check_pages_isolated_cb() always return -EBUSY from > test_pages_isolated(), > > > pfn = __test_page_isolated_in_pageblock(start_pfn, end_pfn, > skip_hwpoisoned_pages); > ... > return pfn < end_pfn ? -EBUSY : 0; > > 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. > > while (pfn < end_pfn) { > ... > else > break; > > 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 += 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 -- Michal Hocko SUSE Labs