Re: [PATCH v5 0/9] mm/memory-failure: keep hardware-poisoned pages out of the next kexec

[Breno Leitao]

Hello Miaohe,

On Tue, Sep 22, 2026 at 02:27:59PM +0800, Miaohe Lin wrote:
> > A bit is never cleared, which is a known limitation: it stands for a
> > whole unit, so an unpoison of one frame cannot tell whether the unit as a
> > whole is good again.
> 
> Thanks for your patches. I have a question about unpoison: If a bit is never
> cleared, after we do some memory-failure+unpoison tests, kexec will lose the
> tested memory without reboot?

Correct, A bit stands for a 2M unit, so every tested page that falls in
a distinct unit costs 2M in each kernel after the kexec.

Worth being precise about the state today: the unpoison itself works.
The frame goes back to the allocator and num_poisoned_pages drops. Only
the bit stays, so the next kernel poisons the frame again. Test loop
in, memory out, and nothing gives it back.

Important to say that nothing block us from unpoison the bitmap, and in
fact my initial patchset had it. I also _think_ we should unpoison the
bitmap once we unpoison the page. 

I have just kept it out of this patch in order to simplify the patchset and
get the basis correct, and then evolve on top of it.

That said, If you think this is a must have in first patchset, I am more
than happy to do it now, but just keep it in mind that it will grow the
patchset by about 2 extra functions.

Thanks the review,
--breno