From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f72.google.com (mail-wm0-f72.google.com [74.125.82.72]) by kanga.kvack.org (Postfix) with ESMTP id 39B856B02EE for ; Fri, 28 Apr 2017 02:51:35 -0400 (EDT) Received: by mail-wm0-f72.google.com with SMTP id l198so8472wmb.20 for ; Thu, 27 Apr 2017 23:51:35 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id y205si2015518wmg.123.2017.04.27.23.51.33 for (version=TLS1 cipher=AES128-SHA bits=128/128); Thu, 27 Apr 2017 23:51:34 -0700 (PDT) Date: Fri, 28 Apr 2017 08:51:31 +0200 From: Michal Hocko Subject: Re: [PATCH v2 2/2] mm: skip HWPoisoned pages when onlining pages Message-ID: <20170428065131.GD8143@dhcp22.suse.cz> References: <1493130472-22843-1-git-send-email-ldufour@linux.vnet.ibm.com> <1493130472-22843-3-git-send-email-ldufour@linux.vnet.ibm.com> <1493172615.4828.3.camel@gmail.com> <20170426031255.GB11619@hori1.linux.bs1.fc.nec.co.jp> <20170428063048.GA9399@dhcp22.suse.cz> <20170428065050.GC8143@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170428065050.GC8143@dhcp22.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Naoya Horiguchi Cc: Balbir Singh , Laurent Dufour , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "akpm@linux-foundation.org" On Fri 28-04-17 08:50:50, Michal Hocko wrote: > [Drop Wen Congyang because his address bounces - we will have to find > out ourselves...] Ble, for real this time. Sorry about spamming > On Fri 28-04-17 08:30:48, Michal Hocko wrote: > > On Wed 26-04-17 03:13:04, Naoya Horiguchi wrote: > > > On Wed, Apr 26, 2017 at 12:10:15PM +1000, Balbir Singh wrote: > > > > On Tue, 2017-04-25 at 16:27 +0200, Laurent Dufour wrote: > > > > > The commit b023f46813cd ("memory-hotplug: skip HWPoisoned page when > > > > > offlining pages") skip the HWPoisoned pages when offlining pages, but > > > > > this should be skipped when onlining the pages too. > > > > > > > > > > Signed-off-by: Laurent Dufour > > > > > --- > > > > > mm/memory_hotplug.c | 4 ++++ > > > > > 1 file changed, 4 insertions(+) > > > > > > > > > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > > > > > index 6fa7208bcd56..741ddb50e7d2 100644 > > > > > --- a/mm/memory_hotplug.c > > > > > +++ b/mm/memory_hotplug.c > > > > > @@ -942,6 +942,10 @@ static int online_pages_range(unsigned long start_pfn, unsigned long nr_pages, > > > > > if (PageReserved(pfn_to_page(start_pfn))) > > > > > for (i = 0; i < nr_pages; i++) { > > > > > page = pfn_to_page(start_pfn + i); > > > > > + if (PageHWPoison(page)) { > > > > > + ClearPageReserved(page); > > > > > > > > Why do we clear page reserved? Also if the page is marked PageHWPoison, it > > > > was never offlined to begin with? Or do you expect this to be set on newly > > > > hotplugged memory? Also don't we need to skip the entire pageblock? > > > > > > If I read correctly, to "skip HWPoiosned page" in commit b023f46813cd means > > > that we skip the page status check for hwpoisoned pages *not* to prevent > > > memory offlining for memblocks with hwpoisoned pages. That means that > > > hwpoisoned pages can be offlined. > > > > Is this patch actually correct? I am trying to wrap my head around it > > but it smells like it tries to avoid the problem rather than fix it > > properly. I might be wrong here of course but to me it sounds like > > poisoned page should simply be offlined and keep its poison state all > > the time. If the memory is hot-removed and added again we have lost the > > struct page along with the state which is the expected behavior. If it > > is still broken we will re-poison it. > > > > Anyway a patch to skip over poisoned pages during online makes perfect > > sense to me. The PageReserved fiddling around much less so. > > > > Or am I missing something. Let's CC Wen Congyang for the clarification > > here. > > -- > Michal Hocko > SUSE Labs -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org