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

[jane . chu]

On 8/25/2025 9:09 AM, Kyle Meyer wrote:
> 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@xxxxxxx> 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@xxxxxxx> 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.

Assuming this means that the numbers reported from
  /sys/devices/system/node/node*/memory_failure/*
do not match certain expectation, right?

If so, could you clarify what is the expectation?

> > > > > 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

Agreed with Miaohe that "None" won't work.
"Process killed" sounds okay for MF_MSG_ALREADY_POISONED, but
we need to understand why "Failed" doesn't work for your usecase.
"Failed" means process is killed but page is not successfully isolated 
which applies to MF_MSG_ALREADY_POISONED case as well.

thanks!
-jane

> Thanks,
> Kyle Meyer