Re: [RFC PATCH v1 4/4] mm, memory_hotplug: fix inconsistent num_poisoned_pages on memory hotremove

From: "HORIGUCHI NAOYA(堀口　直也)" <naoya.horiguchi@nec.com>
To: Miaohe Lin <linmiaohe@huawei.com>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>,
	Andrew Morton <akpm@linux-foundation.org>,
	David Hildenbrand <david@redhat.com>,
	Mike Kravetz <mike.kravetz@oracle.com>,
	Yang Shi <shy828301@gmail.com>,
	Oscar Salvador <osalvador@suse.de>,
	Muchun Song <songmuchun@bytedance.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Linux-MM <linux-mm@kvack.org>
Subject: Re: [RFC PATCH v1 4/4] mm, memory_hotplug: fix inconsistent num_poisoned_pages on memory hotremove
Date: Thu, 28 Apr 2022 04:05:57 +0000	[thread overview]
Message-ID: <20220428040556.GA3945421@hori.linux.bs1.fc.nec.co.jp> (raw)
In-Reply-To: <828cc111-40e8-88ed-bb50-fb185e5f0304@huawei.com>

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@nec.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