Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751426AbdILMt4 (ORCPT ); Tue, 12 Sep 2017 08:49:56 -0400 Received: from mx2.suse.de ([195.135.220.15]:56938 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751289AbdILMty (ORCPT ); Tue, 12 Sep 2017 08:49:54 -0400 Date: Tue, 12 Sep 2017 14:49:52 +0200 From: Michal Hocko To: YASUAKI ISHIMATSU Cc: linux-mm@kvack.org, LKML , qiuxishi@huawei.com, arbab@linux.vnet.ibm.com, Vlastimil Babka Subject: Re: [PATCH] mm/memory_hotplug: fix wrong casting for __remove_section() Message-ID: <20170912124952.uraxdt5bgl25zhf7@dhcp22.suse.cz> References: <51a59ec3-e7ba-2562-1917-036b8181092c@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <51a59ec3-e7ba-2562-1917-036b8181092c@gmail.com> User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2869 Lines: 78 On Fri 08-09-17 16:43:04, YASUAKI ISHIMATSU wrote: > __remove_section() calls __remove_zone() to shrink zone and pgdat. > But due to wrong castings, __remvoe_zone() cannot shrink zone > and pgdat correctly if pfn is over 0xffffffff. > > So the patch fixes the following 3 wrong castings. > > 1. find_smallest_section_pfn() returns 0 or start_pfn which defined > as unsigned long. But the function always returns 32bit value > since the function is defined as int. > > 2. find_biggest_section_pfn() returns 0 or pfn which defined as > unsigned long. the function always returns 32bit value > since the function is defined as int. this is indeed wrong. Pfns over would be really broken 15TB. Not that unrealistic these days > > 3. __remove_section() calculates start_pfn using section_nr_to_pfn() > and scn_nr. section_nr_to_pfn() just shifts scn_nr by > PFN_SECTION_SHIFT bit. But since scn_nr is defined as int, > section_nr_to_pfn() always return 32 bit value. Dohh, those nasty macros. This is hidden quite well. It seems other callers are using unsigned long properly. But I would rather make sure we won't repeat that error again. Can we instead make section_nr_to_pfn resp. pfn_to_section_nr static inline and enfore proper types? I would also split this into two patches. Thanks! > The patch fixes the wrong castings. > > Signed-off-by: Yasuaki Ishimatsu > --- > mm/memory_hotplug.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 73bf17d..3514ef2 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -331,7 +331,7 @@ int __ref __add_pages(int nid, unsigned long phys_start_pfn, > > #ifdef CONFIG_MEMORY_HOTREMOVE > /* find the smallest valid pfn in the range [start_pfn, end_pfn) */ > -static int find_smallest_section_pfn(int nid, struct zone *zone, > +static unsigned long find_smallest_section_pfn(int nid, struct zone *zone, > unsigned long start_pfn, > unsigned long end_pfn) > { > @@ -356,7 +356,7 @@ static int find_smallest_section_pfn(int nid, struct zone *zone, > } > > /* find the biggest valid pfn in the range [start_pfn, end_pfn). */ > -static int find_biggest_section_pfn(int nid, struct zone *zone, > +static unsigned long find_biggest_section_pfn(int nid, struct zone *zone, > unsigned long start_pfn, > unsigned long end_pfn) > { > @@ -544,7 +544,7 @@ static int __remove_section(struct zone *zone, struct mem_section *ms, > return ret; > > scn_nr = __section_nr(ms); > - start_pfn = section_nr_to_pfn(scn_nr); > + start_pfn = section_nr_to_pfn((unsigned long)scn_nr); > __remove_zone(zone, start_pfn); > > sparse_remove_one_section(zone, ms, map_offset); > -- > 1.8.3.1 > -- Michal Hocko SUSE Labs