Re: [PATCH v6 3/7] mm/memory-failure: add hwpoison_boot_page() to flag an inherited frame

[Mike Rapoport <rppt@kernel.org>]

On Fri, Oct 16, 2026 at 05:15:43AM -0700, Breno Leitao wrote:
> A kernel that kexecs inherits the frames its predecessor found
> hardware-poisoned. It has to carry them as PG_hwpoison in its own memmap,
> so that everything that already understands the flag covers them,
> including the kexec segment placement check.
> 
> Add a helper that sets the flag and counts the frame in
> num_poisoned_pages. It runs while the memmap is initialised, before
> memory_dev_init() has run. memblk_nr_poison_inc() divides by
> sections_per_block, which memory_dev_init() sets, so the helper
> increments num_poisoned_pages itself instead of calling
> num_poisoned_pages_inc().
> 
> An inherited frame is a hardware failure like any other, so the helper
> sets hw_memory_failure. Without it, unpoison_memory() accepts the frame,
> clears the flag and drops the last reference, which frees a frame that
> is still bad.
> 
> The helper also counts the frame as managed, as a frame that fails at
> run time stays counted. Memory offlining subtracts every frame of the
> block that is not PageOffline, so a frame that was never counted leaves
> the managed page count too low after an offline.
> 
> The per-node memory failure statistics are not updated. This kernel
> handled no failure, it only inherited one.
> 
> Signed-off-by: Breno Leitao <leitao@debian.org>
> ---
>  mm/internal.h       | 5 +++++
>  mm/memory-failure.c | 8 ++++++++
>  2 files changed, 13 insertions(+)
> 
> diff --git a/mm/internal.h b/mm/internal.h
> index da14c56fb24e11..4bd3bbce86e0ad 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -1169,6 +1169,7 @@ void SetPageHWPoisonTakenOff(struct page *page);
>  void ClearPageHWPoisonTakenOff(struct page *page);
>  bool take_page_off_buddy(struct page *page);
>  bool put_page_back_buddy(struct page *page);
> +void __init hwpoison_boot_page(struct page *page);
>  struct task_struct *task_early_kill(struct task_struct *tsk, int force_early);
>  void add_to_kill_ksm(struct task_struct *tsk, const struct page *p,
>  		     struct vm_area_struct *vma, struct list_head *to_kill,
> @@ -1181,6 +1182,10 @@ static inline int unmap_poisoned_folio(struct folio *folio, unsigned long pfn, b
>  {
>  	return -EBUSY;
>  }
> +
> +static inline void hwpoison_boot_page(struct page *page)
> +{
> +}
>  #endif

We've been splitting internal.h to smaller headers, maybe it's time to add
"memory-faulure.h"?
  
>  extern unsigned long  __must_check vm_mmap_pgoff(struct file *, unsigned long,
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index a2ca8df501caee..d0d6b184ee469f 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -96,6 +96,14 @@ void num_poisoned_pages_sub(unsigned long pfn, long i)
>  		memblk_nr_poison_sub(pfn, i);
>  }
>  
> +void __init hwpoison_boot_page(struct page *page)
> +{
> +	SetPageHWPoison(page);
> +	atomic_long_inc(&num_poisoned_pages);
> +	hw_memory_failure = true;
> +	adjust_managed_page_count(page, 1);
> +}
> +
>  /*
>   * Return the first or the last hardware-poisoned online page in [start,
>   * start + size), or PHYS_ADDR_MAX if the range is clean.
> 
> -- 
> 2.53.0-Meta
> 

-- 
Sincerely yours,
Mike.