On Mon, Jul 10, 2023 at 04:32:27PM +0800, Miaohe Lin wrote:
> On 2023/7/10 15:58, Naoya Horiguchi wrote:
> > On Sat, Jul 08, 2023 at 04:57:44PM +0800, Miaohe Lin wrote:
> >> page_folio() is fetched before calling get_hwpoison_hugetlb_folio()
> >> without hugetlb_lock being held. So hugetlb page could be demoted
> >> before get_hwpoison_hugetlb_folio() holding hugetlb_lock but after
> >> page_folio() is fetched. So get_hwpoison_hugetlb_folio() will hold
> >> unexpected extra refcnt of hugetlb folio while leaving demoted page
> >> un-refcnted.
> >
> > Very nice, thank you for finding the issue.
> >
> >>
> >> Fixes: 25182f05ffed ("mm,hwpoison: fix race with hugetlb page allocation")
> >> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> >> ---
> >> mm/memory-failure.c | 18 ++++++++++++++----
> >> 1 file changed, 14 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> >> index 76d88d27cdbe..066bf57f2d22 100644
> >> --- a/mm/memory-failure.c
> >> +++ b/mm/memory-failure.c
> >> @@ -1388,8 +1388,14 @@ static int __get_hwpoison_page(struct page *page, unsigned long flags)
> >> bool hugetlb = false;
> >>
> >> ret = get_hwpoison_hugetlb_folio(folio, &hugetlb, false);
> >> - if (hugetlb)
> >> - return ret;
> >> + if (hugetlb) {
> >> + if (folio == page_folio(page))
> >> + return ret;
> >
> > Some short comment about the race against demotion here is helpful.
>
> Does the below comment makes sense to you?
>
> "
> Make sure hugetlb demotion did not happen from under us.
> "
Yes, this sounds fine.
Thanks,
Naoya Horiguchi
