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

[jane . chu]

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@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);"?

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

thanks!
-jane
> Thanks.
> .