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=-4.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 6B731C04EB8 for ; Thu, 6 Dec 2018 12:02:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2EFA8208E7 for ; Thu, 6 Dec 2018 12:02:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1544097749; bh=0sLcR5DV8d8KUCA36ww29jHiFNbJ5mjslSYkbMALxKE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=uFkFk+MigpFnpAsLUahY39DCx9g4eny5F3HbmZ2GNtcD5m4vWbsRjDNI1yW3pGJyK 044rV+ZI5wvF9nducILLjh0o3gv6fO7j5mhQe2+Zoh/j5FM5cH/7nDqABNw1H5i8La qUdIrQTDbEdi0odTbpEhF2vFfmhgcggj8RiDkfYk= DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2EFA8208E7 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729515AbeLFMC2 (ORCPT ); Thu, 6 Dec 2018 07:02:28 -0500 Received: from mx2.suse.de ([195.135.220.15]:59452 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728482AbeLFMC1 (ORCPT ); Thu, 6 Dec 2018 07:02:27 -0500 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 CE789AFBB; Thu, 6 Dec 2018 12:02:24 +0000 (UTC) Date: Thu, 6 Dec 2018 13:02:23 +0100 From: Michal Hocko To: Naoya Horiguchi Cc: Oscar Salvador , Andrew Morton , Dan Williams , Pavel Tatashin , "linux-mm@kvack.org" , LKML , Stable tree Subject: Re: [RFC PATCH] hwpoison, memory_hotplug: allow hwpoisoned pages to be offlined Message-ID: <20181206120223.GG1286@dhcp22.suse.cz> References: <20181203100309.14784-1-mhocko@kernel.org> <20181205122918.GL1286@dhcp22.suse.cz> <20181205165716.GS1286@dhcp22.suse.cz> <20181206052137.GA28595@hori1.linux.bs1.fc.nec.co.jp> <20181206083206.GC1286@dhcp22.suse.cz> <20181206091552.GB26516@hori1.linux.bs1.fc.nec.co.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181206091552.GB26516@hori1.linux.bs1.fc.nec.co.jp> 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 Thu 06-12-18 09:15:53, Naoya Horiguchi wrote: > On Thu, Dec 06, 2018 at 09:32:06AM +0100, Michal Hocko wrote: > > On Thu 06-12-18 05:21:38, Naoya Horiguchi wrote: > > > On Wed, Dec 05, 2018 at 05:57:16PM +0100, Michal Hocko wrote: > > > > On Wed 05-12-18 13:29:18, Michal Hocko wrote: > > > > [...] > > > > > After some more thinking I am not really sure the above reasoning is > > > > > still true with the current upstream kernel. Maybe I just managed to > > > > > confuse myself so please hold off on this patch for now. Testing by > > > > > Oscar has shown this patch is helping but the changelog might need to be > > > > > updated. > > > > > > > > OK, so Oscar has nailed it down and it seems that 4.4 kernel we have > > > > been debugging on behaves slightly different. The underlying problem is > > > > the same though. So I have reworded the changelog and added "just in > > > > case" PageLRU handling. Naoya, maybe you have an argument that would > > > > make this void for current upstream kernels. > > > > > > The following commit (not in 4.4.x stable tree) might explain the > > > difference you experienced: > > > > > > commit 286c469a988fbaf68e3a97ddf1e6c245c1446968 > > > Author: Naoya Horiguchi > > > Date: Wed May 3 14:56:22 2017 -0700 > > > > > > mm: hwpoison: call shake_page() after try_to_unmap() for mlocked page > > > > > > This commit adds shake_page() for mlocked pages to make sure that the target > > > page is flushed out from LRU cache. Without this shake_page(), subsequent > > > delete_from_lru_cache() (from me_pagecache_clean()) fails to isolate it and > > > the page will finally return back to LRU list. So this scenario leads to > > > "hwpoisoned by still linked to LRU list" page. > > > > OK, I see. So does that mean that the LRU handling is no longer needed > > and there is a guanratee that all kernels with the above commit cannot > > ever get an LRU page? > > Theoretically no such gurantee, because try_to_unmap() doesn't have a > guarantee of success and then memory_failure() returns immediately > when hwpoison_user_mappings fails. > Or the following code (comes after hwpoison_user_mappings block) also implies > that the target page can still have PageLRU flag. > > /* > * Torn down by someone else? > */ > if (PageLRU(p) && !PageSwapCache(p) && p->mapping == NULL) { > action_result(pfn, MF_MSG_TRUNCATED_LRU, MF_IGNORED); > res = -EBUSY; > goto out; > } > > So I think it's OK to keep "if (WARN_ON(PageLRU(page)))" block in > current version of your patch. > > Feel free to add my ack. > > Acked-by: Naoya Horiguchi Thanks a lot Naoya! I will extend the changelog with your wording. -- Michal Hocko SUSE Labs