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.
"
>
> Anyway, the patch looks good to me.
>
> Acked-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Many thanks for your review and comment, Naoya.
