On 9/15/22 00:39, Doug Berger wrote:
> With gigantic pages it may not be true that struct page structures
> are contiguous across the entire gigantic page. The nth_page macro
> is used here in place of direct pointer arithmetic to correct for
> this.
>
> Fixes: 8531fc6f52f5 ("hugetlb: add hugetlb demote page support")
> Signed-off-by: Doug Berger <opendmb@xxxxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx>
Reviewed-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
> ---
> mm/hugetlb.c | 14 ++++++++------
> 1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index e070b8593b37..0bdfc7e1c933 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -3420,6 +3420,7 @@ static int demote_free_huge_page(struct hstate *h, struct page *page)
> {
> int i, nid = page_to_nid(page);
> struct hstate *target_hstate;
> + struct page *subpage;
> int rc = 0;
>
> target_hstate = size_to_hstate(PAGE_SIZE << h->demote_order);
> @@ -3453,15 +3454,16 @@ static int demote_free_huge_page(struct hstate *h, struct page *page)
> mutex_lock(&target_hstate->resize_lock);
> for (i = 0; i < pages_per_huge_page(h);
> i += pages_per_huge_page(target_hstate)) {
> + subpage = nth_page(page, i);
> if (hstate_is_gigantic(target_hstate))
> - prep_compound_gigantic_page_for_demote(page + i,
> + prep_compound_gigantic_page_for_demote(subpage,
> target_hstate->order);
> else
> - prep_compound_page(page + i, target_hstate->order);
> - set_page_private(page + i, 0);
> - set_page_refcounted(page + i);
> - prep_new_huge_page(target_hstate, page + i, nid);
> - put_page(page + i);
> + prep_compound_page(subpage, target_hstate->order);
> + set_page_private(subpage, 0);
> + set_page_refcounted(subpage);
> + prep_new_huge_page(target_hstate, subpage, nid);
> + put_page(subpage);
> }
> mutex_unlock(&target_hstate->resize_lock);
>
