On 2023/7/10 16:39, Naoya Horiguchi wrote:
> 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.
Will do it in v2. Thanks.
>
> Thanks,
> Naoya Horiguchi
>
> .
>
