[PATCH v2 0/5] hwpoison: fixes on v4.2-rc4

[Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>]

This is v2 of hwpoison fix series for v4.2.
I reflected the feedback for v1, and tried another solution for "reuse just
after soft-offline" problem (see patch 5/5.)

General description (mostly identical to v1)
===================

Recently I addressed a few of hwpoison race problems and the patches are merged
on v4.2-rc1. It made progress, but unfortunately some problems still remain due
to less coverage of my testing. So I'm trying to fix or avoid them in this series.

One point I'm expecting to discuss is that patch 4/5 changes the page flag set
to be checked on free time. In current behavior, __PG_HWPOISON is not supposed
to be set when the page is freed. I think that there is no strong reason for this
behavior, and it causes a problem hard to fix only in error handler side (because
__PG_HWPOISON could be set at arbitrary timing.) So I suggest to change it.

Test
====

With this patchset, hwpoison stress testing in official mce-test testsuite
(which previously failed) passes.

Thanks,
Naoya Horiguchi
---
Tree: https://github.com/Naoya-Horiguchi/linux/tree/v4.2-rc4/hwpoison.v2
---
Summary:

Naoya Horiguchi (5):
      mm/memory-failure: unlock_page before put_page
      mm/memory-failure: fix race in counting num_poisoned_pages
      mm/memory-failure: give up error handling for non-tail-refcounted thp
      mm: check __PG_HWPOISON separately from PAGE_FLAGS_CHECK_AT_*
      mm/memory-failure: set PageHWPoison before migrate_pages()

 include/linux/page-flags.h | 10 +++++++---
 mm/huge_memory.c           |  7 +------
 mm/memory-failure.c        | 32 ++++++++++++++++++--------------
 mm/migrate.c               |  8 ++++++--
 mm/page_alloc.c            |  4 ++++
 5 files changed, 36 insertions(+), 25 deletions(-)
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