Re: [PATCH] mm/memory-failure: Do not call action_result() on already poisoned pages

[Miaohe Lin <linmiaohe@huawei.com>]

On 2025/8/22 8:24, Jiaqi Yan wrote:
> On Thu, Aug 21, 2025 at 12:36 PM Kyle Meyer <kyle.meyer@hpe.com> wrote:
>>
>> On Thu, Aug 21, 2025 at 11:23:48AM -0700, Jiaqi Yan wrote:
>>> On Thu, Aug 21, 2025 at 9:46 AM Kyle Meyer <kyle.meyer@hpe.com> wrote:
>>>>
>>>> Calling action_result() on already poisoned pages causes issues:
>>>>
>>>> * The amount of hardware corrupted memory is incorrectly incremented.
>>>> * NUMA node memory failure statistics are incorrectly updated.
>>>> * Redundant "already poisoned" messages are printed.
>>>
>>> All agreed.
>>>
>>>>
>>>> Do not call action_result() on already poisoned pages and drop unused
>>>> MF_MSG_ALREADY_POISONED.
>>>
>>> Hi Kyle,
>>>
>>> Patch looks great to me, just one thought...

Thanks both.

>>>
>>> Alternatively, have you thought about keeping MF_MSG_ALREADY_POISONED
>>> but changing action_result for MF_MSG_ALREADY_POISONED?
>>> - don't num_poisoned_pages_inc(pfn)
>>> - don't update_per_node_mf_stats(pfn, result)
>>> - still pr_err("%#lx: recovery action for %s: %s\n", ...)
>>> - meanwhile remove "pr_err("%#lx: already hardware poisoned\n", pfn)"
>>> in memory_failure and try_memory_failure_hugetlb
>>
>> I did consider that approach but I was concerned about passing
>> MF_MSG_ALREADY_POISONED to action_result() with MF_FAILED. The message is a
>> bit misleading.
> 
> Based on my reading the documentation for MF_* in static const char
> *action_name[]...
> 
> Yeah, for file mapped pages, kernel may not have hole-punched or
> truncated it from the file mapping (shmem and hugetlbfs for example)
> but that still considered as MF_RECOVERED, so touching a page with
> HWPoison flag doesn't mean that page was failed to be recovered
> previously.
> 
> For pages intended to be taken out of the buddy system, touching a
> page with HWPoison flag does imply it isn't isolated and hence
> MF_FAILED.

There should be other cases that memory_failure failed to isolate the
hwpoisoned pages at first time due to various reasons.

> 
> In summary, seeing the HWPoison flag again doesn't necessarily
> indicate what the recovery result was previously; it only indicate
> kernel won't re-attempt to recover?

Yes, kernel won't re-attempt to or just cannot recover.

> 
>>
>> How about introducing a new MF action result? Maybe MF_NONE? The message could
>> look something like:
> 
> Adding MF_NONE sounds fine to me, as long as we correctly document its
> meaning, which can be subtle.

Adding a new MF action result sounds good to me. But IMHO MF_NONE might not be that suitable
as kill_accessing_process might be called to kill proc in this case, so it's not "NONE".

Thanks.
.