Re: [PATCH v5 21/21] mm/hugetlb: Disable freeing vmemmap if struct page size is not power of two

[Michal Hocko]

On Fri 20-11-20 14:43:25, Muchun Song wrote:
> We only can free the unused vmemmap to the buddy system when the
> size of struct page is a power of two.

Can we actually have !power_of_2 struct pages?

> 
> Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
> ---
>  mm/hugetlb_vmemmap.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
> index c3b3fc041903..7bb749a3eea2 100644
> --- a/mm/hugetlb_vmemmap.c
> +++ b/mm/hugetlb_vmemmap.c
> @@ -671,7 +671,8 @@ void __init hugetlb_vmemmap_init(struct hstate *h)
>  	unsigned int order = huge_page_order(h);
>  	unsigned int vmemmap_pages;
>  
> -	if (hugetlb_free_vmemmap_disabled) {
> +	if (hugetlb_free_vmemmap_disabled ||
> +	    !is_power_of_2(sizeof(struct page))) {
>  		pr_info("disable free vmemmap pages for %s\n", h->name);
>  		return;
>  	}
> -- 
> 2.11.0
> 

-- 
Michal Hocko
SUSE Labs