linux-kernel - Re: [PATCH] mm/memory-failure: Do not call action

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Message-ID: <aKyKort2opfQYqgA@hpe.com>
Date: Mon, 25 Aug 2025 11:09:06 -0500
From: Kyle Meyer <kyle.meyer@....com>
To: Miaohe Lin <linmiaohe@...wei.com>
Cc: Jiaqi Yan <jiaqiyan@...gle.com>, akpm@...ux-foundation.org,
        david@...hat.com, tony.luck@...el.com, bp@...en8.de,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-edac@...r.kernel.org, lorenzo.stoakes@...cle.com,
        Liam.Howlett@...cle.com, vbabka@...e.cz, rppt@...nel.org,
        surenb@...gle.com, mhocko@...e.com, nao.horiguchi@...il.com,
        jane.chu@...cle.com, osalvador@...e.de
Subject: Re: [PATCH] mm/memory-failure: Do not call action_result() on
 already poisoned pages

On Mon, Aug 25, 2025 at 11:04:43AM +0800, Miaohe Lin wrote:
> On 2025/8/22 8:24, Jiaqi Yan wrote:
> > On Thu, Aug 21, 2025 at 12:36 PM Kyle Meyer <kyle.meyer@....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@....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".

OK, would you like a separate MF action result for each case? Maybe
MF_ALREADY_POISONED and MF_ALREADY_POISONED_KILLED?

MF_ALREADY_POISONED can be the default and MF_ALREADY_POISONED_KILLED can be
used when kill_accessing_process() returns -EHWPOISON.

The log messages could look like...

Memory failure: 0xXXXXXXXX: recovery action for already poisoned page: None
	and
Memory failure: 0xXXXXXXXX: recovery action for already poisoned page: Process killed

Thanks,
Kyle Meyer