linux-kernel - Re: [PATCH v5 4/4] mm/hwpoison: introduce per-memory

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Message-ID: <20221007005223.GC3227576@hori.linux.bs1.fc.nec.co.jp>
Date:   Fri, 7 Oct 2022 00:52:23 +0000
From:   HORIGUCHI NAOYA(堀口　直也) 
        <naoya.horiguchi@....com>
To:     David Hildenbrand <david@...hat.com>
CC:     Naoya Horiguchi <naoya.horiguchi@...ux.dev>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Yang Shi <shy828301@...il.com>,
        Oscar Salvador <osalvador@...e.de>,
        Muchun Song <songmuchun@...edance.com>,
        Jane Chu <jane.chu@...cle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 4/4] mm/hwpoison: introduce per-memory_block hwpoison
 counter counter

On Mon, Sep 26, 2022 at 10:05:05AM +0200, David Hildenbrand wrote:
> >   /*
> > @@ -2414,6 +2417,10 @@ int unpoison_memory(unsigned long pfn)
> >   unlock_mutex:
> >   	mutex_unlock(&mf_mutex);
> >   	if (!ret || freeit) {
> > +		/*
> > +		 * TODO: per-memory_block counter might break when the page
> > +		 * size to be unpoisoned is larger than a memory_block.
> > +		 */
> 
> Hmm, but that happens easily e.g., with 1 GiB hugetlb page and 128 MiB
> memory section/block size. What would be the right thing to do here? The
> TODO should rather spell that out instead of just stating the problem.

What should we need here is to cancel the per-memory_block hwpoison counts
in each memory block associated with the hugepage to be unpoisoned.
I found that it can be done with additional several lines of code, so
v6 will contain them.  Then, this TODO comment is no longer needed.

Thanks,
Naoya Horiguchi