linux-kernel - Re: [PATCH] mm/sparse: use __nr_to_section(section_nr) to get mem

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Date:   Fri, 9 Aug 2019 13:46:24 +0000
From:   Wei Yang <richard.weiyang@...il.com>
To:     Anshuman Khandual <anshuman.khandual@....com>
Cc:     Wei Yang <richardw.yang@...ux.intel.com>,
        akpm@...ux-foundation.org, osalvador@...e.de,
        pasha.tatashin@...cle.com, mhocko@...e.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/sparse: use __nr_to_section(section_nr) to get
 mem_section

On Fri, Aug 09, 2019 at 02:39:59PM +0530, Anshuman Khandual wrote:
>
>
>On 08/09/2019 06:32 AM, Wei Yang wrote:
>> __pfn_to_section is defined as __nr_to_section(pfn_to_section_nr(pfn)).
>
>Right.
>
>> 
>> Since we already get section_nr, it is not necessary to get mem_section
>> from start_pfn. By doing so, we reduce one redundant operation.
>> 
>> Signed-off-by: Wei Yang <richardw.yang@...ux.intel.com>
>
>Looks right.
>
>With this applied, memory hot add still works on arm64.

Thanks for your test.

>
>Reviewed-by: Anshuman Khandual <anshuman.khandual@....com>
>
>> ---
>>  mm/sparse.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/mm/sparse.c b/mm/sparse.c
>> index 72f010d9bff5..95158a148cd1 100644
>> --- a/mm/sparse.c
>> +++ b/mm/sparse.c
>> @@ -867,7 +867,7 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn,
>>  	 */
>>  	page_init_poison(pfn_to_page(start_pfn), sizeof(struct page) * nr_pages);
>>  
>> -	ms = __pfn_to_section(start_pfn);
>> +	ms = __nr_to_section(section_nr);
>>  	set_section_nid(section_nr, nid);
>>  	section_mark_present(ms);
>>  
>> 

-- 
Wei Yang
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