| From | Luis Henriques <> | Subject | [PATCH 3.5 12/88] mm/memory-failure.c: recheck PageHuge() after hugetlb page migrate successfully | Date | Fri, 7 Feb 2014 11:22:09 +0000 |
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3.5.7.30 -stable review patch. If anyone has any objections, please let me know.
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From: Jianguo Wu <wujianguo@huawei.com>
commit a49ecbcd7b0d5a1cda7d60e03df402dd0ef76ac8 upstream.
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().
BUG: unable to handle kernel NULL pointer dereference at 0000000000000058 IP: [<ffffffff81163761>] dequeue_hwpoisoned_huge_page+0x131/0x1d0 PGD c23762067 PUD c24be2067 PMD 0 Oops: 0000 [#1] SMP
So check PageHuge(page) after call migrate_pages() successfully.
Signed-off-by: Jianguo Wu <wujianguo@huawei.com> Tested-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> [wujg: backport to 3.4: - adjust context - s/num_poisoned_pages/mce_bad_pages/] Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- mm/memory-failure.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-)
diff --git a/mm/memory-failure.c b/mm/memory-failure.c index 1bf1092..5eb3f727 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -1447,10 +1447,18 @@ static int soft_offline_huge_page(struct page *page, int flags) return ret; } done: - if (!PageHWPoison(hpage)) - atomic_long_add(1 << compound_trans_order(hpage), &mce_bad_pages); - set_page_hwpoison_huge_page(hpage); - dequeue_hwpoisoned_huge_page(hpage); + /* overcommit hugetlb page will be freed to buddy */ + if (PageHuge(hpage)) { + if (!PageHWPoison(hpage)) + atomic_long_add(1 << compound_trans_order(hpage), + &mce_bad_pages); + set_page_hwpoison_huge_page(hpage); + dequeue_hwpoisoned_huge_page(hpage); + } else { + SetPageHWPoison(page); + atomic_long_inc(&mce_bad_pages); + } + /* keep elevated page count for bad page */ return ret; } -- 1.8.3.2
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