Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   Dmitry Yakunin <zeil@yandex-team.ru>
To:     osalvador@suse.de
Cc:     linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        mhocko@kernel.org, mike.kravetz@oracle.com,
        n-horiguchi@ah.jp.nec.com, max7255@yandex-team.ru
Subject: Re: [RFC PATCH v2 00/16] Hwpoison rework {hard,soft}-offline
Date:   Thu, 11 Jun 2020 19:43:19 +0300
Message-Id: <20200611164319.16860-1-zeil@yandex-team.ru>
In-Reply-To: <20191017142123.24245-1-osalvador@suse.de>
References: <20191017142123.24245-1-osalvador@suse.de>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Hello!

We are faced with similar problems with hwpoisoned pages
on one of our production clusters after kernel update to stable 4.19.
Application that does a lot of memory allocations sometimes caught SIGBUS signal
with message in dmesg about hardware memory corruption fault.
In kernel and mce logs we saw messages about soft offlining pages with
correctable errors. Those events always had happened before application
was killed. This is not the behavior we expect. We want our application to
continue working on a smaller set of available pages in the system.

This issue is difficult to reproduce, but we suppose that the reason for such
behavior is that compaction does not check for page poisonness while processing
free pages, so as a result valid userspace data gets migrated to bad pages.
We wrote the simple test:
  - soft offline first 4 pages in every 64 continuous pages in ZONE_NORMAL
    through writing pfn to /sys/devices/system/memory/soft_offline_page
  - force compaction by echo 1 >> /proc/sys/vm/compact_memory
Without this patch series after these steps bash became unusable
and every attempt to run any command leads to SIGBUS with message about
hardware memory corruption fault. And after applying this series to our kernel
tree we cannot reproduce such SIGBUSes by our test. On upstream kernel 5.7
this behavior is still reproducible.

So, we want to know, why this patchset wasn't merged to the upstream?
Is there any problems in such rework for {soft,hard}-offline handling?
BTW, this patchset should be updated with upstream changes in mm.

Thanks for you replies.

--
Dmitry Yakunin