linux-kernel - Re: [PATCH v3 00/15] HWPOISON: soft offline rework

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Date:   Wed, 24 Jun 2020 22:36:18 +0000
From:   HORIGUCHI NAOYA(堀口　直也) 
        <naoya.horiguchi@....com>
To:     Andrew Morton <akpm@...ux-foundation.org>
CC:     "nao.horiguchi@...il.com" <nao.horiguchi@...il.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "mhocko@...nel.org" <mhocko@...nel.org>,
        "mike.kravetz@...cle.com" <mike.kravetz@...cle.com>,
        "osalvador@...e.de" <osalvador@...e.de>,
        "tony.luck@...el.com" <tony.luck@...el.com>,
        "david@...hat.com" <david@...hat.com>,
        "aneesh.kumar@...ux.vnet.ibm.com" <aneesh.kumar@...ux.vnet.ibm.com>,
        "zeil@...dex-team.ru" <zeil@...dex-team.ru>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 00/15] HWPOISON: soft offline rework

On Wed, Jun 24, 2020 at 12:17:42PM -0700, Andrew Morton wrote:
> On Wed, 24 Jun 2020 15:01:22 +0000 nao.horiguchi@...il.com wrote:
> 
> > I rebased soft-offline rework patchset [1][2] onto the latest mmotm.  The
> > rebasing required some non-trivial changes to adjust, but mainly that was
> > straightforward.  I confirmed that the reported problem doesn't reproduce on
> > compaction after soft offline.  For more precise description of the problem
> > and the motivation of this patchset, please see [2].
> > 
> > I think that the following two patches in v2 are better to be done with
> > separate work of hard-offline rework, so it's not included in this series.
> > 
> >   - mm,hwpoison: Take pages off the buddy when hard-offlining
> >   - mm/hwpoison-inject: Rip off duplicated checks
> > 
> > These two are not directly related to the reported problem, so they seems
> > not urgent.  And the first one breaks num_poisoned_pages counting in some
> > testcases, and The second patch needs more consideration about commented point.
> > 
> 
> It would be nice to have some sort of overview of the patch series in
> this [0/n] email.
> 
> > [1] v1: https://lore.kernel.org/linux-mm/1541746035-13408-1-git-send-email-n-horiguchi@ah.jp.nec.com/
> > [2] v2: https://lore.kernel.org/linux-mm/20191017142123.24245-1-osalvador@suse.de/
> 
> The above have such, but are they up to date?

The description of the problem doesn't change, but there're some new patches
and some patches are postponed, so I should've added an overview of this series:

- patch 1, 2 are cleanups.
- patch 3, 4, 5 change the precondition when calling memory_failure(). Previously
  we sometimes call it with holding refcount of the target page and somtimes call
  without holding it, and we passed a flag of whether refcount was taken out of
  memory_failure().  It was confusing and caused code more complex than needed.
- patch 6-10 are cleanups.
- patch 11 introduces new logic to remove the error page from buddy allocator,
  which is also applied to the path of soft-offling in-use pages in patch 12.
- patch 13 is basically a refactoring but I added some adjustment to make sure
  that the freed page is surely sent back to buddy instead of being kept in pcplist,
  which is based on discussion in v2.
- patch 14 fixes the inconsistency of return values between injection interfaces.
- patch 15 is a new patch to complement missing code found in code review for
  previous version.

Core change is in patch 11 and 12, and the others are kind of cleanup/refactoring.

Thanks,
Naoya Horiguchi