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

Lance Yang
2026-04-27T15:14:35Z

On 2026/4/27 22:45, Breno Leitao wrote:
> 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);

Works for me, thanks.