Re: [RFC PATCH 3/6] mm: page_owner: add support for splitting to any order in split page_owner.

[Matthew Wilcox]

On Wed, Nov 11, 2020 at 03:40:05PM -0500, Zi Yan wrote:
> -     for (i = 0; i < nr; i++) {
> +     for (i = 0; i < nr; i += (1 << new_order)) {
>               page_owner = get_page_owner(page_ext);
> -             page_owner->order = 0;
> +             page_owner->order = new_order;
>               page_ext = page_ext_next(page_ext);
>       }

This doesn't do what you're hoping it will.  It's going to set ->order to
new_order for the first N pages instead of every 1/N pages.

You'll need to do something like

                page_ext = lookup_page_ext(page + i);

or add a new page_ext_add(page_ext, 1 << new_order);