Re: hwpoison, shmem: fix data lost issue for 5.15.y

From: Mike Kravetz <mike.kravetz@oracle.com>
To: "HORIGUCHI NAOYA(堀口　直也)" <naoya.horiguchi@nec.com>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>,
	Greg KH <gregkh@linuxfoundation.org>,
	"stable@vger.kernel.org" <stable@vger.kernel.org>,
	Yang Shi <shy828301@gmail.com>,
	James Houghton <jthoughton@google.com>,
	Muchun Song <songmuchun@bytedance.com>,
	Miaohe Lin <linmiaohe@huawei.com>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: hwpoison, shmem: fix data lost issue for 5.15.y
Date: Tue, 22 Nov 2022 17:05:07 -0800	[thread overview]
Message-ID: <Y31xw1DcqXGx86Fz@monkey> (raw)
In-Reply-To: <20221115011646.GA767662@hori.linux.bs1.fc.nec.co.jp>

On 11/15/22 01:16, HORIGUCHI NAOYA(堀口 直也) wrote:
> On Mon, Nov 14, 2022 at 02:53:51PM -0800, Mike Kravetz wrote:
> > On 11/15/22 07:39, Naoya Horiguchi wrote:
> > > On Mon, Nov 14, 2022 at 05:11:35PM +0100, Greg KH wrote:
> > > > On Mon, Nov 14, 2022 at 10:14:03PM +0900, Naoya Horiguchi wrote:
> > > > > Hi,
> > > > > 
> > > > > I'd like to request the follow commits to be backported to 5.15.y.
> > > > > 
> > > > > - dd0f230a0a80 ("mm: hwpoison: refactor refcount check handling")
> > > > > - 4966455d9100 ("mm: hwpoison: handle non-anonymous THP correctly")
> > > > > - a76054266661 ("mm: shmem: don't truncate page if memory failure happens")
> > > > > 
> > > > > These patches fixed a data lost issue by preventing shmem pagecache from
> > > > > being removed by memory error.  These were not tagged for stable originally,
> > > > > but that's revisited recently.
> > > > 
> > > > And have you tested that these all apply properly (and in which order?)
> > > 
> > > Yes, I've checked that these cleanly apply (without any change) on
> > > 5.15.78 in the above order (i.e. dd0f23 is first, 496645 comes next,
> > > then a76054).
> > > 
> > > > and work correctly?
> > > 
> > > Yes, I ran related testcases in my test suite, and their status changed
> > > FAIL to PASS with these patches.
> > 
> > Hi Naoya,
> > 
> > Just curious if you have plans to do backports for earlier releases?
> 
> I didn't have a clear plan.  I just thought that we should backport to
> earlier kernels if someone want and the patches are applicable easily
> enough and well-tested.
> 
> > 
> > If not, I can start that effort.  We have seen data loss/corruption because of
> > this on a 4.14 based release.   So, I would go at least that far back.
> 
> Thank you for raising hand, that's really helpful.
> 
> Maybe dd0f230a0a80 ("[PATCH] hugetlbfs: don't delete error page from
> pagecbache") should be considered to backport together, because it's
> the similar issue and reported (a while ago) to fail to backport.
> dd0f230a0a80 does not apply cleanly on top of 5.15.78 + the above 3 patches.
> So I need check more and will update my current proposal for 5.15.y.

When working with 5.10.y, I noticed that commit eac96c3efdb5 ("mm: filemap:
check if THP has hwpoisoned subpage for PMD page fault") as well as the
prereq commit c7cb42e94473 ("mm: hwpoison: remove the unnecessary THP check")
were not backported to 5.10.y.  Without those patches, THP testing will
fail.

Naoya and Yang Shi, does that sound right?

I have backports for those as well but want to check if you think
anything else is needed.
-- 
Mike Kravetz