On Tue, May 12, 2026 at 10:17:00AM +0200, David Hildenbrand (Arm) wrote:
> > @@ -2348,6 +2348,7 @@ int memory_failure(unsigned long pfn, int flags)
> > unsigned long page_flags;
> > bool retry = true;
> > int hugetlb = 0;
> > + bool is_reserved;
> >
> > if (!sysctl_memory_failure_recovery)
> > panic("Memory failure on page %lx", pfn);
> > @@ -2411,6 +2412,18 @@ int memory_failure(unsigned long pfn, int flags)
> > * In fact it's dangerous to directly bump up page count from 0,
> > * that may make page_ref_freeze()/page_ref_unfreeze() mismatch.
> > */
> > + /*
> > + * Pages with PG_reserved set are not currently managed by the
> > + * page allocator (memblock-reserved memory, driver reservations,
> > + * etc.), so classify them as kernel-owned for reporting.
> > + *
> > + * Sample the flag before get_hwpoison_page(): in the
> > + * MF_COUNT_INCREASED path, get_any_page() can drop the caller's
> > + * reference before returning -EIO, after which page->flags may
> > + * have been reset by the allocator.
> > + */
> > + is_reserved = PageReserved(p);
> > +
> > res = get_hwpoison_page(p, flags);
> > if (!res) {
> > if (is_free_buddy_page(p)) {
> > @@ -2432,7 +2445,11 @@ int memory_failure(unsigned long pfn, int flags)
> > }
> > goto unlock_mutex;
> > } else if (res < 0) {
> > - res = action_result(pfn, MF_MSG_GET_HWPOISON, MF_IGNORED);
> > + if (is_reserved)
> > + res = action_result(pfn, MF_MSG_KERNEL, MF_IGNORED);
> > + else
> > + res = action_result(pfn, MF_MSG_GET_HWPOISON,
> > + MF_IGNORED);
> > goto unlock_mutex;
> > }
> >
> >
>
> It's a bit odd that we need this handling when we already have handling for
> reserved pages in error_states[].
>
> HWPoisonHandlable() would always essentially reject PG_reserved pages. So
> __get_hwpoison_page() ... would always fail? Making
> get_hwpoison_page()->get_any_page() always fail?
>
> But then, we never call identify_page_state()? And never call me_kernel()?
>From what I read, it seems that error_states[0] = { reserved, reserved,
>MF_MSG_KERNEL, me_kernel }
has been effectively dead code on the hwpoison-from-MCE path for a
while.
My v6 patch relabels the failure-path output to match what me_kernel() would
have reported anyway.
> This all looks very odd.
>
> Why would you even want to call get_hwpoison_page() in the first place if you
> find PageReserved?
Are you suggesting we should all the page action as soon as we detect the page
is reserved and get out?
Something as:
if (PageReserved(p)) {
res = action_result(pfn, MF_MSG_KERNEL, MF_IGNORED);
goto unlock_mutex;
}
res = get_hwpoison_page(p, flags);
Thanks for the review,
--breno
