Re: [PATCH v5 1/4] mm/memory-failure: report MF_MSG_KERNEL for reserved pages

Breno Leitao
2026-04-27T14:46:05Z

On Mon, Apr 27, 2026 at 08:33:30PM +0800, Lance Yang wrote:
>
> On Fri, Apr 24, 2026 at 05:23:59AM -0700, Breno Leitao wrote:
> >When get_hwpoison_page() returns a negative value, distinguish
> >reserved pages from other failure cases by reporting MF_MSG_KERNEL
> >instead of MF_MSG_GET_HWPOISON. Reserved pages belong to the kernel
> >and should be classified accordingly for proper handling.
> >
> >Acked-by: Miaohe Lin <linmiaohe@huawei.com>
> >Signed-off-by: Breno Leitao <leitao@debian.org>
> >---
> > mm/memory-failure.c | 11 ++++++++++-
> > 1 file changed, 10 insertions(+), 1 deletion(-)
> >
> >diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> >index ee42d43613097..7b67e43dafbd1 100644
> >--- a/mm/memory-failure.c
> >+++ b/mm/memory-failure.c
> >@@ -2432,7 +2432,16 @@ 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);
> >+ /*
> >+ * PageReserved is stable here: reserved pages have
> >+ * PG_reserved set at boot or by drivers and are never
> >+ * freed through the page allocator.
> >+ */
>
> Not necessarily. PG_reserved is not a permanent lifetime property for
> every page that has carried it.
>
> page-flags.h says early reserved pages may later have PG_reserved
> cleared and then be given to the page allocator :)
>
> At least some drivers also clear PG_reserved when releasing pages they
> marked reserved.
>
> Would it be clearer to say that pages with PG_reserved set are not
> currently managed by the page allocator, rather than saying reserved
> pages are never freed through the page allocator?

Would a comment like the following look better?

/*
* 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.
*/
if (PageReserved(p))
res = action_result(pfn, MF_MSG_KERNEL, MF_IGNORED);

Thanks for the review,
--breno