Re: [PATCH] mm/memory-failure: teach kill_accessing_process to accept hugetlb tail page pfn

[jane.chu@oracle.com]

On 12/19/2025 12:01 AM, Miaohe Lin wrote:
> On 2025/12/19 14:28, Jane Chu wrote:
>> When a hugetlb folio is being poisoned again, try_memory_failure_hugetlb()
>> passed head pfn to kill_accessing_process(), that is not right.
>> The precise pfn of the poisoned page should be used in order to
>> determine the precise vaddr as the SIGBUS payload.
>>
>> This issue has already been taken care of in the normal path, that is,
>> hwpoison_user_mappings(), see [1][2].  Further more, for [3] to work
>> correctly in the hugetlb repoisoning case, it's essential to inform
>> VM the precise poisoned page, not the head page.
>>
>> [1] https://lkml.kernel.org/r/20231218135837.3310403-1-willy@infradead.org
>> [2] https://lkml.kernel.org/r/20250224211445.2663312-1-jane.chu@oracle.com
>> [3] https://lore.kernel.org/lkml/20251116013223.1557158-1-jiaqiyan@google.com/
>>
> 
> Thanks for your patch.
> 
>> Cc: <stable@vger.kernel.org>
>> Signed-off-by: Jane Chu <jane.chu@oracle.com>
>> ---
>>   mm/memory-failure.c | 22 ++++++++++++----------
>>   1 file changed, 12 insertions(+), 10 deletions(-)
>>
>> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
>> index 3edebb0cda30..c9d87811b1ea 100644
>> --- a/mm/memory-failure.c
>> +++ b/mm/memory-failure.c
>> @@ -681,9 +681,11 @@ static void set_to_kill(struct to_kill *tk, unsigned long addr, short shift)
>>   }
>>   
>>   static int check_hwpoisoned_entry(pte_t pte, unsigned long addr, short shift,
>> -				unsigned long poisoned_pfn, struct to_kill *tk)
>> +				unsigned long poisoned_pfn, struct to_kill *tk,
>> +				int pte_nr)
>>   {
>>   	unsigned long pfn = 0;
>> +	unsigned long hwpoison_vaddr;
>>   
>>   	if (pte_present(pte)) {
>>   		pfn = pte_pfn(pte);
>> @@ -694,10 +696,11 @@ static int check_hwpoisoned_entry(pte_t pte, unsigned long addr, short shift,
>>   			pfn = swp_offset_pfn(swp);
>>   	}
>>   
>> -	if (!pfn || pfn != poisoned_pfn)
>> +	if (!pfn || (pfn > poisoned_pfn || (pfn + pte_nr - 1) < poisoned_pfn))
>>   		return 0;
> 
> Can we get pte_nr from @shift? I.e. something like "pte_nr = 1UL << (shift - PAGE_SHIFT);"?

Why?  Is there any concern with using the macro pages_per_huge_page(h) ?

thanks!
-jane
> 
> Thanks.
> .