On Thu, Aug 06, 2020 at 06:49:11PM +0000, nao.horiguchi@gmail.com wrote:

Hi,

This patchset is the latest version of soft offline rework patchset
targetted for v5.9.

Since v5, I dropped some patches which tweak refcount handling in
madvise_inject_error() to avoid the "unknown refcount page" error.
I don't confirm the fix (that didn't reproduce with v5 in my environment),
but this change surely call soft_offline_page() after holding refcount,
so the error should not happen any more.

With this patchset, arm64 is still suffering from premature 512M-size hugepages
allocation failures.

# git clone https://gitlab.com/cailca/linux-mm
# cd linux-mm; make
# ./random 1
- start: migrate_huge_offline
- use NUMA nodes 0,1.
- mmap and free 2147483648 bytes hugepages on node 0
- mmap and free 2147483648 bytes hugepages on node 1
madvise: Cannot allocate memory

[  292.456538][ T3685] soft offline: 0x8a000: hugepage isolation failed: 0, page count 2, type 7ffff80001000e (referenced|uptodate|dirty|head)
[  292.469113][ T3685] Soft offlining pfn 0x8c000 at process virtual address 0xffff60000000
[  292.983855][ T3685] Soft offlining pfn 0x88000 at process virtual address 0xffff40000000
[  293.271369][ T3685] Soft offlining pfn 0x8a000 at process virtual address 0xffff60000000
[  293.834030][ T3685] Soft offlining pfn 0xa000 at process virtual address 0xffff40000000
[  293.851378][ T3685] soft offline: 0xa000: hugepage migration failed -12, type 7ffff80001000e (referenced|uptodate|dirty|head)

The fresh-booted system still had 40G+ memory free before running the test.

Reverting the following commits allowed the test to run succesfully over and over again.

"mm, hwpoison: remove recalculating hpage"
"mm,hwpoison-inject: don't pin for hwpoison_filter"
"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"

i.e., it is not enough to only revert,

mm,hwpoison: double-check page count in __get_any_page()
mm,hwpoison: introduce MF_MSG_UNSPLIT_THP
mm,hwpoison: return 0 if the page is already poisoned in soft-offline

Dropped patches
- mm,madvise: call soft_offline_page() without MF_COUNT_INCREASED
- mm,madvise: Refactor madvise_inject_error
- mm,hwpoison: remove MF_COUNT_INCREASED
- mm,hwpoison: remove flag argument from soft offline functions

Thanks,
Naoya Horiguchi

Quoting cover letter of v5:
----
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.

---
Previous versions:
  v1: https://lore.kernel.org/linux-mm/1541746035-13408-1-git-send-email-n-horiguchi@ah.jp.nec.com/ (local)
  v2: https://lore.kernel.org/linux-mm/20191017142123.24245-1-osalvador@suse.de/ (local)
  v3: https://lore.kernel.org/linux-mm/20200624150137.7052-1-nao.horiguchi@gmail.com/ (local)
  v4: https://lore.kernel.org/linux-mm/20200716123810.25292-1-osalvador@suse.de/ (local)
  v5: https://lore.kernel.org/linux-mm/20200805204354.GA16406@hori.linux.bs1.fc.nec.co.jp/T/#t (local)
---
Summary:

Naoya Horiguchi (5):
      mm,hwpoison: cleanup unused PageHuge() check
      mm, hwpoison: remove recalculating hpage
      mm,hwpoison-inject: don't pin for hwpoison_filter
      mm,hwpoison: introduce MF_MSG_UNSPLIT_THP
      mm,hwpoison: double-check page count in __get_any_page()

Oscar Salvador (7):
      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

 include/linux/mm.h         |   3 +-
 include/linux/page-flags.h |   6 +-
 include/ras/ras_event.h    |   3 +
 mm/hwpoison-inject.c       |  18 +--
 mm/madvise.c               |   5 -
 mm/memory-failure.c        | 307 +++++++++++++++++++++------------------------
 mm/migrate.c               |  11 +-
 mm/page_alloc.c            |  60 +++++++--
 8 files changed, 203 insertions(+), 210 deletions(-)

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