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

[Oscar Salvador <osalvador@suse.de>]

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).

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