Re: [patch 13/15] mm/page_owner: align with pageblock_nr pages

[zhong jiang <zhongjiang@huawei.com>]

On 2017/12/4 20:35, Michal Hocko wrote:
> On Mon 04-12-17 20:23:49, zhong jiang wrote:
>> On 2017/12/4 20:01, Michal Hocko wrote:
>>> On Mon 04-12-17 19:51:12, zhong jiang wrote:
>>>> On 2017/12/2 1:15, Michal Hocko wrote:
>>>>> On Fri 01-12-17 17:58:28, Vlastimil Babka wrote:
>>>>>> On 11/30/2017 11:15 PM, akpm@linux-foundation.org wrote:
>>>>>>> From: zhong jiang <zhongjiang@huawei.com>
>>>>>>> Subject: mm/page_owner: align with pageblock_nr pages
>>>>>>>
>>>>>>> When pfn_valid(pfn) returns false, pfn should be aligned with
>>>>>>> pageblock_nr_pages other than MAX_ORDER_NR_PAGES in init_pages_in_zone,
>>>>>>> because the skipped 2M may be valid pfn, as a result, early allocated
>>>>>>> count will not be accurate.
>>>>>>>
>>>>>>> Link: http://lkml.kernel.org/r/1468938136-24228-1-git-send-email-zhongjiang@huawei.com
>>>>>>> Signed-off-by: zhong jiang <zhongjiang@huawei.com>
>>>>>>> Cc: Michal Hocko <mhocko@kernel.org>
>>>>>>> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
>>>>>> The author never responded and Michal Hocko basically NAKed it in
>>>>>> https://lkml.kernel.org/r/<20160812130727.GI3639@dhcp22.suse.cz>
>>>>>> I think we should drop it.
>>>>> Or extend the changelog to actually describe what kind of problem it
>>>>> fixes and do an additional step to unigy
>>>>> MAX_ORDER_NR_PAGES/pageblock_nr_pages
>>>>>  
>>>>   Hi, Michal
>>>>    
>>>>         IIRC,  I had explained the reason for patch.  if it not. I am so sorry for that.
>>>>     
>>>>         when we select MAX_ORDER_NR_PAGES,   the second 2M will be skiped.
>>>>        it maybe result in normal pages leak.
>>>>
>>>>         meanwhile.  as you had said.  it make the code consistent.  why do not we do it.
>>>>    
>>>>         I think it is reasonable to upstream the patch.  maybe I should rewrite the changelog
>>>>        and repost it.
>>>>
>>>>     Michal,  Do you think ?
>>> Yes, rewrite the patch changelog and make it _clear_ what it fixes and
>>> under _what_ conditions. There are also other places using
>>> MAX_ORDER_NR_PAGES rathern than pageblock_nr_pages. Do they need to be
>>> updated as well?
>>  in the lastest kernel.  according to correspond context,   I  can not find the candidate. :-)
> git grep says some in page_ext.c, memory_hotplug.c and few in the arch
> code. I belive we really want to describe and document the distinction
> between the two constants and explain when to use which one.
>
 yes,   limited by my knowledge and english.  Maybe Vlastimil  can  address it  in detail.  

Thanks
zhongjiang

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