linux-kernel - Re: [RFC PATCH v1 4/4] mm, memory_hotplug: fix inconsistent num_poisoned

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Message-ID: <20220428040556.GA3945421@hori.linux.bs1.fc.nec.co.jp>
Date:   Thu, 28 Apr 2022 04:05:57 +0000
From:   HORIGUCHI NAOYA(堀口　直也) 
        <naoya.horiguchi@....com>
To:     Miaohe Lin <linmiaohe@...wei.com>
CC:     Naoya Horiguchi <naoya.horiguchi@...ux.dev>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Yang Shi <shy828301@...il.com>,
        Oscar Salvador <osalvador@...e.de>,
        Muchun Song <songmuchun@...edance.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>
Subject: Re: [RFC PATCH v1 4/4] mm, memory_hotplug: fix inconsistent
 num_poisoned_pages on memory hotremove

On Thu, Apr 28, 2022 at 11:20:16AM +0800, Miaohe Lin wrote:
> On 2022/4/27 12:28, Naoya Horiguchi wrote:
> > From: Naoya Horiguchi <naoya.horiguchi@....com>
> > 
> > When offlining memory section with hwpoisoned pages, the hwpoisons are
> > canceled. But num_poisoned_pages is not updated for that event, so the
> > counter becomes inconsistent.
> 
> IIUC, this work is already done via clear_hwpoisoned_pages when __remove_pages.
> Or am I miss something?

Actually I had the same question when writing this patch, and found that
__remove_pages() seems to be called from device memory or HMM, but not from
offline_pages().  If you mean that we could make offline_pages() call
clear_hwpoisoned_pages(), that seems possible and I'll consider it.

But as David and Oscar pointed out for 0/4, removing PageHWPoison flags
in offlining seems not to be right thing, so I'd like to have some consensus
on what way to go first.

Thanks,
Naoya Horiguchi