linux-kernel - Re: [PATCH v5 2/2] mm/memory-failure: teach kill_accessing

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Message-ID: <cd880ec7-b433-4534-ac1e-4c5af4bea462@oracle.com>
Date: Thu, 15 Jan 2026 10:17:38 -0800
From: jane.chu@...cle.com
To: Miaohe Lin <linmiaohe@...wei.com>
Cc: linux-mm@...ck.org, stable@...r.kernel.org, muchun.song@...ux.dev,
        osalvador@...e.de, david@...nel.org, jiaqiyan@...gle.com,
        william.roche@...cle.com, rientjes@...gle.com,
        akpm@...ux-foundation.org, lorenzo.stoakes@...cle.com,
        Liam.Howlett@...cle.com, rppt@...nel.org, surenb@...gle.com,
        mhocko@...e.com, willy@...radead.org, clm@...a.com,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 2/2] mm/memory-failure: teach kill_accessing_process to
 accept hugetlb tail page pfn



On 1/14/2026 11:36 PM, Miaohe Lin wrote:
> On 2026/1/15 5:37, 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/
>>
>> Cc: <stable@...r.kernel.org>
>> Signed-off-by: Jane Chu <jane.chu@...cle.com>
>> Reviewed-by: Liam R. Howlett <Liam.Howlett@...cle.com>
>> ---
>> v5, v4: No change.
>> v2 -> v3:
>>    incorporated suggestions from Miaohe and Matthew.
>> v1 -> v2:
>>    pickup R-B, add stable to cc list.
>> ---
>>   mm/memory-failure.c | 14 ++++++++------
>>   1 file changed, 8 insertions(+), 6 deletions(-)
>>
>> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
>> index 2563718c34c6..f6b806499caa 100644
>> --- a/mm/memory-failure.c
>> +++ b/mm/memory-failure.c
>> @@ -692,6 +692,8 @@ static int check_hwpoisoned_entry(pte_t pte, unsigned long addr, short shift,
>>   				unsigned long poisoned_pfn, struct to_kill *tk)
>>   {
>>   	unsigned long pfn = 0;
>> +	unsigned long hwpoison_vaddr;
>> +	unsigned long mask;
>>   
>>   	if (pte_present(pte)) {
>>   		pfn = pte_pfn(pte);
>> @@ -702,10 +704,12 @@ static int check_hwpoisoned_entry(pte_t pte, unsigned long addr, short shift,
>>   			pfn = softleaf_to_pfn(entry);
>>   	}
>>   
>> -	if (!pfn || pfn != poisoned_pfn)
>> +	mask = ~((1UL << (shift - PAGE_SHIFT)) - 1);
>> +	if (!pfn || ((pfn & mask) != (poisoned_pfn & mask)))
>>   		return 0;
> 
> Nit: Maybe "(!pfn || pfn != (poisoned_pfn & mask))" is enough?

That's nicer.

> 
> Acked-by: Miaohe Lin <linmiaohe@...wei.com>

Thanks!
-jane

> 
> Thanks.
> .
>