mm: skip HWPoisoned pages when onlining pages

b023f468 ("memory-hotplug: skip HWPoisoned page when offlining pages")
skipped the HWPoisoned pages when offlining pages, but this should be
skipped when onlining the pages too.

n-horiguchi@ah.jp.nec.com said:

: If I read correctly, to "skip HWPoiosned page" in commit b023f468
: means that we skip the page status check for hwpoisoned pages *not* to
: prevent memory offlining for memblocks with hwpoisoned pages.  That
: means that hwpoisoned pages can be offlined.
:
: And another reason to clear PageReserved is that we could reuse the
: hwpoisoned page after onlining back with replacing the broken DIMM.  In
: this usecase, we first do unpoisoning to clear PageHWPoison, but it
: doesn't work if PageReserved is set.  My simple testing shows the BUG
: below in unpoisoning (without the ClearPageReserved):
:
:   Unpoison: Software-unpoisoned page 0x18000
:   BUG: Bad page state in process page-types  pfn:18000
:   page:ffffda5440600000 count:0 mapcount:0 mapping:          (null) index:0x70006b599
:   flags: 0x1fffc00004081a(error|uptodate|dirty|reserved|swapbacked)
:   raw: 001fffc00004081a 0000000000000000 000000070006b599 00000000ffffffff
:   raw: dead000000000100 dead000000000200 0000000000000000 0000000000000000
:   page dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set
:   bad because of flags: 0x800(reserved)

Link: http://lkml.kernel.org/r/1493130472-22843-3-git-send-email-ldufour@linux.vnet.ibm.com


Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andrey Vagin <avagin@openvz.org>
Cc: Glauber Costa <glommer@openvz.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>