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mm/hugetlb: correct demote page offset logic

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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@gmail.com
Fixes: 8531fc6f52 ("hugetlb: add hugetlb demote page support")
Signed-off-by: Doug Berger <opendmb@gmail.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Doug Berger 2022-09-14 12:09:17 -07:00 committed by Andrew Morton
parent dac22531bb
commit 317314527d
1 changed files with 8 additions and 6 deletions
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14
mm/hugetlb.c
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@ -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);