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Date:   Mon, 3 Aug 2020 08:39:55 -0400
From:   Qian Cai <cai@lca.pw>
To:     nao.horiguchi@gmail.com
Cc:     linux-mm@kvack.org, mhocko@kernel.org, akpm@linux-foundation.org,
        mike.kravetz@oracle.com, osalvador@suse.de, tony.luck@intel.com,
        david@redhat.com, aneesh.kumar@linux.vnet.ibm.com,
        zeil@yandex-team.ru, naoya.horiguchi@nec.com,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 00/16] HWPOISON: soft offline rework
Message-ID: <20200803123954.GA4631@lca.pw>
References: <20200731122112.11263-1-nao.horiguchi@gmail.com>
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On Fri, Jul 31, 2020 at 12:20:56PM +0000, nao.horiguchi@gmail.com wrote:
> This patchset is the latest version of soft offline rework patchset
> targetted for v5.9.
> 
> Main focus of this series is to stabilize soft offline.  Historically soft
> offlined pages have suffered from racy conditions because PageHWPoison is
> used to a little too aggressively, which (directly or indirectly) invades
> other mm code which cares little about hwpoison.  This results in unexpected
> behavior or kernel panic, which is very far from soft offline's "do not
> disturb userspace or other kernel component" policy.
> 
> Main point of this change set is to contain target page "via buddy allocator",
> where we first free the target page as we do for normal pages, and remove
> from buddy only when we confirm that it reaches free list. There is surely
> race window of page allocation, but that's fine because someone really want
> that page and the page is still working, so soft offline can happily give up.
> 
> v4 from Oscar tries to handle the race around reallocation, but that part
> seems still work in progress, so I decide to separate it for changes into
> v5.9.  Thank you for your contribution, Oscar.
> 
> The issue reported by Qian Cai is fixed by patch 16/16.

I am still getting EIO everywhere on next-20200803 (which includes this v5).

# ./random 1
- start: migrate_huge_offline
- use NUMA nodes 0,8.
- mmap and free 8388608 bytes hugepages on node 0
- mmap and free 8388608 bytes hugepages on node 8
madvise: Input/output error

From the serial console,

[  637.164222][ T8357] soft offline: 0x118ee0: hugepage isolation failed: 0, page count 2, type 7fff800001000e (referenced|uptodate|dirty|head)
[  637.164890][ T8357] Soft offlining pfn 0x20001380 at process virtual address 0x7fff9f000000
[  637.165422][ T8357] Soft offlining pfn 0x3ba00 at process virtual address 0x7fff9f200000
[  637.166409][ T8357] Soft offlining pfn 0x201914a0 at process virtual address 0x7fff9f000000
[  637.166833][ T8357] Soft offlining pfn 0x12b9a0 at process virtual address 0x7fff9f200000
[  637.168044][ T8357] Soft offlining pfn 0x1abb60 at process virtual address 0x7fff9f000000
[  637.168557][ T8357] Soft offlining pfn 0x20014820 at process virtual address 0x7fff9f200000
[  637.169493][ T8357] Soft offlining pfn 0x119720 at process virtual address 0x7fff9f000000
[  637.169603][ T8357] soft offline: 0x119720: hugepage isolation failed: 0, page count 2, type 7fff800001000e (referenced|uptodate|dirty|head)
[  637.169756][ T8357] Soft offlining pfn 0x118ee0 at process virtual address 0x7fff9f200000
[  637.170653][ T8357] Soft offlining pfn 0x200e81e0 at process virtual address 0x7fff9f000000
[  637.171067][ T8357] Soft offlining pfn 0x201c5f60 at process virtual address 0x7fff9f200000
[  637.172101][ T8357] Soft offlining pfn 0x201c8f00 at process virtual address 0x7fff9f000000
[  637.172241][ T8357] __get_any_page: 0x201c8f00: unknown zero refcount page type 87fff8000000000

> 
> This patchset is based on v5.8-rc7-mmotm-2020-07-27-18-18, but I applied
> this series after reverting previous version.
> Maybe https://github.com/Naoya-Horiguchi/linux/commits/soft-offline-rework.v5
> shows what I did more precisely.
> 
> Any other comment/suggestion/help would be appreciated.
> 
> Thanks,
> Naoya Horiguchi
> ---
> Previous versions:
>   v1: https://lore.kernel.org/linux-mm/1541746035-13408-1-git-send-email-n-horiguchi@ah.jp.nec.com/
>   v2: https://lore.kernel.org/linux-mm/20191017142123.24245-1-osalvador@suse.de/
>   v3: https://lore.kernel.org/linux-mm/20200624150137.7052-1-nao.horiguchi@gmail.com/
>   v4: https://lore.kernel.org/linux-mm/20200716123810.25292-1-osalvador@suse.de/
> ---
> Summary:
> 
> Naoya Horiguchi (8):
>       mm,hwpoison: cleanup unused PageHuge() check
>       mm, hwpoison: remove recalculating hpage
>       mm,madvise: call soft_offline_page() without MF_COUNT_INCREASED
>       mm,hwpoison-inject: don't pin for hwpoison_filter
>       mm,hwpoison: remove MF_COUNT_INCREASED
>       mm,hwpoison: remove flag argument from soft offline functions
>       mm,hwpoison: introduce MF_MSG_UNSPLIT_THP
>       mm,hwpoison: double-check page count in __get_any_page()
> 
> Oscar Salvador (8):
>       mm,madvise: Refactor madvise_inject_error
>       mm,hwpoison: Un-export get_hwpoison_page and make it static
>       mm,hwpoison: Kill put_hwpoison_page
>       mm,hwpoison: Unify THP handling for hard and soft offline
>       mm,hwpoison: Rework soft offline for free pages
>       mm,hwpoison: Rework soft offline for in-use pages
>       mm,hwpoison: Refactor soft_offline_huge_page and __soft_offline_page
>       mm,hwpoison: Return 0 if the page is already poisoned in soft-offline
> 
>  drivers/base/memory.c      |   2 +-
>  include/linux/mm.h         |  12 +-
>  include/linux/page-flags.h |   6 +-
>  include/ras/ras_event.h    |   3 +
>  mm/hwpoison-inject.c       |  18 +--
>  mm/madvise.c               |  39 +++---
>  mm/memory-failure.c        | 334 ++++++++++++++++++++-------------------------
>  mm/migrate.c               |  11 +-
>  mm/page_alloc.c            |  60 ++++++--
>  9 files changed, 233 insertions(+), 252 deletions(-)