Re: Widespread boot failures on ARM due to "mm/page_alloc.c: calculate zone_start_pfn at zone_spanned_pages_in_node()"

[Sudeep Holla <sudeep.holla@arm.com>]

On 05/01/16 19:59, Steve Capper wrote:
> On 5 January 2016 at 12:21, Sudeep Holla <sudeep.holla@arm.com> wrote:
>>
>>
>> On 05/01/16 11:45, Mark Brown wrote:
>>>
>>> On Mon, Jan 04, 2016 at 04:35:28PM -0800, Andrew Morton wrote:
>>>>
>>>> On Mon, 4 Jan 2016 23:55:12 +0000 Mark Brown <broonie@kernel.org> wrote:
>>>>>
>>>>> On Mon, Jan 04, 2016 at 03:09:46PM -0800, Andrew Morton wrote:
>>>
>>>
>>>>>> Thanks.  That patch has rather a blooper if
>>>>>> CONFIG_HAVE_MEMBLOCK_NODE_MAP=n.  Is that the case in your testing?
>>>
>>>
>>>>> Seems to be what's making a difference from a quick run through, yes.
>>>
>>>
>>>> OK, thanks.
>>>
>>>
>>> Seems like I was mistaken here somehow or there's some other problem -
>>> I've kicked off another bisect for today's -next:
>>>
>>>
>>> https://ci.linaro.org/view/people/job/tbaker-boot-bisect-bot/137/console
>>>
>>> and will follow up with any results.
>>>
>>
>> With both patches applied(one already in today's -next), I am able to
>> boot on ARM64 platform but I get huge load(for each pfn) of below warning:
>>
>> -->8
>>
>> BUG: Bad page state in process swapper  pfn:900000
>> page:ffffffbde4000000 count:0 mapcount:1 mapping: (null) index:0x0
>> flags: 0x0()
>> page dumped because: nonzero mapcount
>> Modules linked in:
>> Hardware name: ARM Juno development board (r0) (DT)
>> Call trace:
>> [<ffffffc000089830>] dump_backtrace+0x0/0x180
>> [<ffffffc0000899c4>] show_stack+0x14/0x20
>> [<ffffffc000335008>] dump_stack+0x90/0xc8
>> [<ffffffc0001531f8>] bad_page+0xd8/0x138
>> [<ffffffc000153470>] free_pages_prepare+0x218/0x290
>> [<ffffffc000154d4c>] __free_pages_ok+0x1c/0xb8
>> [<ffffffc000155638>] __free_pages+0x30/0x50
>> [<ffffffc00092fa9c>] __free_pages_bootmem+0xa0/0xa8
>> [<ffffffc0009321d0>] free_all_bootmem+0x11c/0x184
>> [<ffffffc000925264>] mem_init+0x48/0x1b4
>> [<ffffffc0009217e0>] start_kernel+0x224/0x3b4
>> [<0000000080663000>] 0x80663000
>> Disabling lock debugging due to kernel taint
>>
>> --
>
> I managed to get 904769ac82ebf60cb54f225f59ae7c064772a4d7 booting on
> an arm64 machine without errors with the following changes:
>
> =====================================
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index a8bb70d..0edb608 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -5013,6 +5013,15 @@ static inline unsigned long __meminit
> zone_spanned_pages_in_node(int nid,
>                                          unsigned long *zone_end_pfn,
>                                          unsigned long *zones_size)
>   {
> +       unsigned int zone;
> +
> +       *zone_start_pfn = node_start_pfn;
> +       for (zone = 0; zone < zone_type; zone++) {
> +               *zone_start_pfn += zones_size[zone];
> +       }
> +
> +       *zone_end_pfn = *zone_start_pfn + zones_size[zone_type];
> +
>          return zones_size[zone_type];
>   }
>
> @@ -5328,6 +5337,8 @@ void __paginginit free_area_init_node(int nid,
> unsigned long *zones_size,
>          pr_info("Initmem setup node %d [mem %#018Lx-%#018Lx]\n", nid,
>                  (u64)start_pfn << PAGE_SHIFT,
>                  end_pfn ? ((u64)end_pfn << PAGE_SHIFT) - 1 : 0);
> +#else
> +       start_pfn = node_start_pfn;
>   #endif
>          calculate_node_totalpages(pgdat, start_pfn, end_pfn,
>                                    zones_size, zholes_size);
>
> =====================================
>
> My understanding is that 904769a ("mm/page_alloc.c: calculate
> zone_start_pfn at zone_spanned_pages_in_node()") inadvertently
> discards information when pgdat->node_start_pfn is removed from
> free_area_init_core (and zone_start_pfn is no longer updated by "size"
> in the loop inside free_area_init_core). This isn't an issue with
> systems where CONFIG_HAVE_MEMBLOCK_NODE_MAP is enabled as
> zone_start_pfn is set correctly. On systems without
> CONFIG_HAVE_MEMBLOCK_NODE_MAP, zone_start_pfn is always 0.
>
> When I ported the above fix to linux-next
> (8ef79cd05e6894c01ab9b41aa918a402fa8022a7) I was able to boot in a VM
> but not on my actual machine, I'll investigate that tomorrow.
>

It fixes the issue on real hardware too(Juno).

-- 
Regards,
Sudeep