On 5/13/26 17:39, Breno Leitao wrote:
> The first entry of error_states[],
>
> { reserved, reserved, MF_MSG_KERNEL, me_kernel },
>
> is unreachable. identify_page_state() has two callers, and neither
> one can dispatch a PG_reserved page to me_kernel():
>
> * memory_failure() reaches identify_page_state() only after
> get_hwpoison_page() returned 1. get_any_page() reaches that
> return only via __get_hwpoison_page(), which gates the refcount
> on HWPoisonHandlable(). HWPoisonHandlable() rejects PG_reserved
> pages, so they fail with -EBUSY/-EIO long before
> identify_page_state() runs.
You should clarify why they are rejected. There is no explicit check for
PG_reserved in there!
>
> * try_memory_failure_hugetlb() reaches identify_page_state() on
> the MF_HUGETLB_IN_USED branch, but the page is necessarily a
> hugetlb folio there. The first table entry that matches a
> hugetlb folio is { head, head, MF_MSG_HUGE, me_huge_page }, so
> they dispatch to me_huge_page() before the (now-removed)
> reserved entry would have matched, regardless of whether
> PG_reserved happens to be set on the head page.
See hugetlb_folio_init_vmemmap(): we always clear PG_reserved for hugetlb folios
allocated from memblock.
>
> me_kernel() never executes and the entry exists only to be matched
> against by code that cannot see it.
>
> Drop the entry, the me_kernel() helper, and the now-unused
> "reserved" macro. Leave the MF_MSG_KERNEL enum value in place: it
> remains part of the tracepoint and pr_err() string tables, and
> follow-on work to classify unrecoverable kernel pages can reuse it
> without churning the user-visible enum.
>
> No functional change.
>
> Suggested-by: David Hildenbrand <[email protected]>
> Signed-off-by: Breno Leitao <[email protected]>
> ---
> mm/memory-failure.c | 14 --------------
> 1 file changed, 14 deletions(-)
>
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 866c4428ac7ef..49bcfbd04d213 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -992,17 +992,6 @@ static bool has_extra_refcount(struct page_state *ps,
> struct page *p,
> return false;
> }
>
> -/*
> - * Error hit kernel page.
> - * Do nothing, try to be lucky and not touch this instead. For a few cases we
> - * could be more sophisticated.
> - */
> -static int me_kernel(struct page_state *ps, struct page *p)
> -{
> - unlock_page(p);
> - return MF_IGNORED;
> -}
> -
> /*
> * Page in unknown state. Do nothing.
> * This is a catch-all in case we fail to make sense of the page state.
> @@ -1211,10 +1200,8 @@ static int me_huge_page(struct page_state *ps, struct
> page *p)
> #define mlock (1UL << PG_mlocked)
> #define lru (1UL << PG_lru)
> #define head (1UL << PG_head)
> -#define reserved (1UL << PG_reserved)
>
> static struct page_state error_states[] = {
> - { reserved, reserved, MF_MSG_KERNEL, me_kernel },
> /*
> * free pages are specially detected outside this table:
> * PG_buddy pages only make a small fraction of all free pages.
> @@ -1246,7 +1233,6 @@ static struct page_state error_states[] = {
> #undef mlock
> #undef lru
> #undef head
> -#undef reserved
>
> static void update_per_node_mf_stats(unsigned long pfn,
> enum mf_result result)
>
Yes, I think this should work.
Acked-by: David Hildenbrand (Arm) <[email protected]>
--
Cheers,
David
