From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt0-f199.google.com (mail-qt0-f199.google.com [209.85.216.199]) by kanga.kvack.org (Postfix) with ESMTP id 1F2186B0038 for ; Tue, 12 Sep 2017 13:05:46 -0400 (EDT) Received: by mail-qt0-f199.google.com with SMTP id m35so14053654qte.1 for ; Tue, 12 Sep 2017 10:05:46 -0700 (PDT) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id a65sor4535758qkd.118.2017.09.12.10.05.43 for (Google Transport Security); Tue, 12 Sep 2017 10:05:43 -0700 (PDT) Subject: Re: [PATCH] mm/memory_hotplug: fix wrong casting for __remove_section() References: <51a59ec3-e7ba-2562-1917-036b8181092c@gmail.com> <20170912124952.uraxdt5bgl25zhf7@dhcp22.suse.cz> From: YASUAKI ISHIMATSU Message-ID: <587bdecd-2584-21be-94b8-61b427f1b0e8@gmail.com> Date: Tue, 12 Sep 2017 13:05:39 -0400 MIME-Version: 1.0 In-Reply-To: <20170912124952.uraxdt5bgl25zhf7@dhcp22.suse.cz> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: linux-mm@kvack.org, LKML , qiuxishi@huawei.com, arbab@linux.vnet.ibm.com, Vlastimil Babka , yasu.isimatu@gmail.com Hi Michal, Thanks you for reviewing my patch. On 09/12/2017 08:49 AM, Michal Hocko wrote: > 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 Why 15TB? Actually, all callers use pfn which defined as unsigned long to receive the return value of find_{smallest|biggest}_section_nr(). So it will break over 16TB. > >> >> 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'll update it. > > I would also split this into two patches. I'll update it. Thanks, Yasuaki Ishimatsu > > 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 >> > -- 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