From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f72.google.com (mail-pg0-f72.google.com [74.125.83.72]) by kanga.kvack.org (Postfix) with ESMTP id 08DA46B0009 for ; Thu, 26 Apr 2018 15:11:17 -0400 (EDT) Received: by mail-pg0-f72.google.com with SMTP id x205so7591592pgx.19 for ; Thu, 26 Apr 2018 12:11:17 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id f1-v6si19257735pld.168.2018.04.26.12.11.15 for (version=TLS1 cipher=AES128-SHA bits=128/128); Thu, 26 Apr 2018 12:11:15 -0700 (PDT) Date: Thu, 26 Apr 2018 21:11:11 +0200 From: Michal Hocko Subject: Re: [PATCH] mm: sections are not offlined during memory hotremove Message-ID: <20180426191111.GV17484@dhcp22.suse.cz> References: <20180426155834.16845-1-pasha.tatashin@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180426155834.16845-1-pasha.tatashin@oracle.com> Sender: owner-linux-mm@kvack.org List-ID: To: Pavel Tatashin Cc: steven.sistare@oracle.com, daniel.m.jordan@oracle.com, akpm@linux-foundation.org, kirill.shutemov@linux.intel.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org On Thu 26-04-18 11:58:34, Pavel Tatashin wrote: > Memory hotplug, and hotremove operate with per-block granularity. If > machine has large amount of memory (more than 64G), the size of memory > block can span multiple sections. By mistake, during hotremove we set > only the first section to offline state. > > The bug was discovered because kernel selftest started to fail: > https://lkml.kernel.org/r/20180423011247.GK5563@yexl-desktop > > After commit, "mm/memory_hotplug: optimize probe routine". But, the bug is > older than this commit. In this optimization we also added a check for > sections to be in a proper state during hotplug operation. > > Fixes: 2d070eab2e82 ("mm: consider zone which is not fully populated to have holes") Dohh. When I saw this I've had that feeling that I have fixed this already and it must have get lost somewhere. But no, this was the same bug in a different path b4ccec41af82 ("mm/sparse.c: fix typo in online_mem_sections"). I wonder why I haven't noticed the same pattern in the offline path. Thanks for noticing and fixing this. > Signed-off-by: Pavel Tatashin Acked-by: Michal Hocko > --- > mm/sparse.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/sparse.c b/mm/sparse.c > index 62eef264a7bd..73dc2fcc0eab 100644 > --- a/mm/sparse.c > +++ b/mm/sparse.c > @@ -629,7 +629,7 @@ void offline_mem_sections(unsigned long start_pfn, unsigned long end_pfn) > unsigned long pfn; > > for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) { > - unsigned long section_nr = pfn_to_section_nr(start_pfn); > + unsigned long section_nr = pfn_to_section_nr(pfn); > struct mem_section *ms; > > /* > -- > 1.8.3.1 > -- Michal Hocko SUSE Labs