Re: [PATCH v3 1/6] mm/memory-hotplug: fix lowmem count overflow when offline pages

[Wanpeng Li <liwanp@linux.vnet.ibm.com>]

On Sun, May 26, 2013 at 07:49:33AM -0400, KOSAKI Motohiro wrote:
>On Sun, May 26, 2013 at 1:58 AM, Wanpeng Li <liwanp@linux.vnet.ibm.com> wrote:
>> Changelog:
>>  v1 -> v2:
>>         * show number of HighTotal before hotremove
>>         * remove CONFIG_HIGHMEM
>>         * cc stable kernels
>>         * add Michal reviewed-by
>>
>> Logic memory-remove code fails to correctly account the Total High Memory
>> when a memory block which contains High Memory is offlined as shown in the
>> example below. The following patch fixes it.
>>
>> Stable for 2.6.24+.
>>
>> Before logic memory remove:
>>
>> MemTotal:        7603740 kB
>> MemFree:         6329612 kB
>> Buffers:           94352 kB
>> Cached:           872008 kB
>> SwapCached:            0 kB
>> Active:           626932 kB
>> Inactive:         519216 kB
>> Active(anon):     180776 kB
>> Inactive(anon):   222944 kB
>> Active(file):     446156 kB
>> Inactive(file):   296272 kB
>> Unevictable:           0 kB
>> Mlocked:               0 kB
>> HighTotal:       7294672 kB
>> HighFree:        5704696 kB
>> LowTotal:         309068 kB
>> LowFree:          624916 kB
>>
>> After logic memory remove:
>>
>> MemTotal:        7079452 kB
>> MemFree:         5805976 kB
>> Buffers:           94372 kB
>> Cached:           872000 kB
>> SwapCached:            0 kB
>> Active:           626936 kB
>> Inactive:         519236 kB
>> Active(anon):     180780 kB
>> Inactive(anon):   222944 kB
>> Active(file):     446156 kB
>> Inactive(file):   296292 kB
>> Unevictable:           0 kB
>> Mlocked:               0 kB
>> HighTotal:       7294672 kB
>> HighFree:        5181024 kB
>> LowTotal:       4294752076 kB
>> LowFree:          624952 kB
>>
>> Reviewed-by: Michal Hocko <mhocko@suse.cz>
>> Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
>> ---
>>  mm/page_alloc.c | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index 98cbdf6..23b921f 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -6140,6 +6140,8 @@ __offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
>>                 list_del(&page->lru);
>>                 rmv_page_order(page);
>>                 zone->free_area[order].nr_free--;
>> +               if (PageHighMem(page))
>> +                       totalhigh_pages -= 1 << order;
>>                 for (i = 0; i < (1 << order); i++)
>>                         SetPageReserved((page+i));
>>                 pfn += (1 << order);
>
>Hm. I already NAKed and you didn't answered my question. isn't it?

Jiang makes his effort to support highmem for memory hotremove, he also
fix this bug, http://marc.info/?l=linux-mm&m=136957578620221&w=2

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