Re: [PATCH v5 2/2] mm/memory-failure: teach kill_accessing_process to accept hugetlb tail page pfn

[Miaohe Lin <linmiaohe@huawei.com>]

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@vger.kernel.org>
> Signed-off-by: Jane Chu <jane.chu@oracle.com>
> Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.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?

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

Thanks.
.