Re: [PATCH v2] mm/sparse: set section nid for hot-add memory

[Oscar Salvador <osalvador@suse.de>]

On Tue, Jun 18, 2019 at 08:55:37AM +0800, Wei Yang wrote:
> In case of NODE_NOT_IN_PAGE_FLAGS is set, we store section's node id in
> section_to_node_table[]. While for hot-add memory, this is missed.
> Without this information, page_to_nid() may not give the right node id.
> 
> BTW, current online_pages works because it leverages nid in memory_block.
> But the granularity of node id should be mem_section wide.

I forgot to ask this before, but why do you mention online_pages here?
IMHO, it does not add any value to the changelog, and it does not have much
to do with the matter.

online_pages() works with memblock granularity and not section granularity.
That memblock is just a hot-added range of memory, worth of either 1 section or multiple
sections, depending on the arch or on the size of the current memory.
And we assume that each hot-added memory all belongs to the same node.


> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
> Reviewed-by: Oscar Salvador <osalvador@suse.de>
> Reviewed-by: David Hildenbrand <david@redhat.com>
> Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
> 
> ---
> v2:
>   * specify the case NODE_NOT_IN_PAGE_FLAGS is effected.
>   * list one of the victim page_to_nid()
> 
> ---
>  mm/sparse.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/mm/sparse.c b/mm/sparse.c
> index 4012d7f50010..48fa16038cf5 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -733,6 +733,7 @@ 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