From: Doug Berger <opendmb@xxxxxxxxx> commit 317314527d173e1f139ceaf8cb87cb1746abf240 upstream. 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. Mike said: : This error could cause addressing exceptions. However, this is only : possible in configurations where CONFIG_SPARSEMEM && : !CONFIG_SPARSEMEM_VMEMMAP. Such a configuration option is rare and : unknown to be the default anywhere. Link: https://lkml.kernel.org/r/20220914190917.3517663-1-opendmb@xxxxxxxxx Fixes: 8531fc6f52f5 ("hugetlb: add hugetlb demote page support") Signed-off-by: Doug Berger <opendmb@xxxxxxxxx> Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx> Reviewed-by: Oscar Salvador <osalvador@xxxxxxx> Reviewed-by: Anshuman Khandual <anshuman.khandual@xxxxxxx> Cc: Muchun Song <songmuchun@xxxxxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- mm/hugetlb.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -3418,6 +3418,7 @@ static int demote_free_huge_page(struct { 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); @@ -3451,15 +3452,16 @@ static int demote_free_huge_page(struct 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);
