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

[Miaohe Lin]

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@xxxxxxxxxxxxx
> [2] https://lkml.kernel.org/r/20250224211445.2663312-1-jane.chu@xxxxxxxxxx
> [3] https://lore.kernel.org/lkml/20251116013223.1557158-1-jiaqiyan@xxxxxxxxxx/
> 

Thanks for your patch.

> Cc: <stable@xxxxxxxxxxxxxxx>
> Signed-off-by: Jane Chu <jane.chu@xxxxxxxxxx>
> ---
>  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);"?

Thanks.
.