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Subject[PATCH] mm/memory-failure.c: recheck PageHuge() after hugetlb page migrate successfully
Changelog:
- Only set PageHWPoison on the error raw page if page is freed into buddy

After a successful hugetlb page migration by soft offline, the source page
will either be freed into hugepage_freelists or buddy(over-commit page).
If page is in buddy, page_hstate(page) will be NULL. It will hit a NULL
pointer dereference in dequeue_hwpoisoned_huge_page().

[ 890.677918] BUG: unable to handle kernel NULL pointer dereference at
0000000000000058
[ 890.685741] IP: [<ffffffff81163761>]
dequeue_hwpoisoned_huge_page+0x131/0x1d0
[ 890.692861] PGD c23762067 PUD c24be2067 PMD 0
[ 890.697314] Oops: 0000 [#1] SMP

So check PageHuge(page) after call migrate_pages() successfully.

Tested-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: stable@vger.kernel.org
Signed-off-by: Jianguo Wu <wujianguo@huawei.com>
---
mm/memory-failure.c | 14 ++++++++++----
1 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index b7c1716..db08af9 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1505,10 +1505,16 @@ static int soft_offline_huge_page(struct page *page, int flags)
if (ret > 0)
ret = -EIO;
} else {
- set_page_hwpoison_huge_page(hpage);
- dequeue_hwpoisoned_huge_page(hpage);
- atomic_long_add(1 << compound_order(hpage),
- &num_poisoned_pages);
+ /* overcommit hugetlb page will be freed to buddy */
+ if (PageHuge(page)) {
+ set_page_hwpoison_huge_page(hpage);
+ dequeue_hwpoisoned_huge_page(hpage);
+ atomic_long_add(1 << compound_order(hpage),
+ &num_poisoned_pages);
+ } else {
+ SetPageHWPoison(page);
+ atomic_long_inc(&num_poisoned_pages);
+ }
}
return ret;
}
--
1.7.1



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