Re: [PATCH] mm/sparse: set section nid for hot-add memory

[Wei Yang <richardw.yang@linux.intel.com>]

On Mon, Jun 17, 2019 at 05:43:25PM +0200, Oscar Salvador wrote:
>On Sun, Jun 16, 2019 at 10:35:54AM +0800, Wei Yang wrote:
>> section_to_node_table[] is used to record section's node id, which is
>> used in page_to_nid(). While for hot-add memory, this is missed.
>> 
>> BTW, current online_pages works because it leverages nid in memory_block.
>> But the granularity of node id should be mem_section wide.
>> 
>> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
>
>While the patch is valid, I think that the changelog could be improved a bit.
>For example, I would point out the possible problems we can face if it is not set
>properly (e.g: page_to_nid() operations failing to give the right node) and when
>section_to_node_table[] is used (NODE_NOT_IN_PAGE_FLAGS scenario).
>

Thanks, let me give more words on this.

>Reviewed-by: Oscar Salvador <osalvador@suse.de>
>
>> ---
>>  mm/sparse.c | 1 +
>>  1 file changed, 1 insertion(+)
>> 
>> diff --git a/mm/sparse.c b/mm/sparse.c
>> index fd13166949b5..3ba8f843cb7a 100644
>> --- a/mm/sparse.c
>> +++ b/mm/sparse.c
>> @@ -735,6 +735,7 @@ int __meminit sparse_add_one_section(int nid, unsigned long start_pfn,
>>  	 */
>>  	page_init_poison(memmap, sizeof(struct page) * PAGES_PER_SECTION);
>>  
>> +	set_section_nid(section_nr, nid);
>>  	section_mark_present(ms);
>>  	sparse_init_one_section(ms, section_nr, memmap, usemap);
>>  
>> -- 
>> 2.19.1
>> 
>
>-- 
>Oscar Salvador
>SUSE L3

-- 
Wei Yang
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