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Date: Mon, 1 Apr 2013 13:21:22 -0400 From: Naoya Horiguchi <n-horiguchi@...jp.nec.com> To: Andrew Morton <akpm@...ux-foundation.org> Cc: Mel Gorman <mgorman@...e.de>, Hugh Dickins <hughd@...gle.com>, Rik van Riel <riel@...hat.com>, KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>, Konstantin Khlebnikov <khlebnikov@...nvz.org>, Michal Hocko <mhocko@...e.cz>, linux-mm@...ck.org, linux-kernel@...r.kernel.org, stable@...r.kernel.org Subject: [PATCH v2 2/2] hugetlbfs: add swap entry check in follow_hugetlb_page() With applying the previous patch "hugetlbfs: stop setting VM_DONTDUMP in initializing vma(VM_HUGETLB)" to reenable hugepage coredump, if a memory error happens on a hugepage and the affected processes try to access the error hugepage, we hit VM_BUG_ON(atomic_read(&page->_count) <= 0) in get_page(). The reason for this bug is that coredump-related code doesn't recognise "hugepage hwpoison entry" with which a pmd entry is replaced when a memory error occurs on a hugepage. In other words, physical address information is stored in different bit layout between hugepage hwpoison entry and pmd entry, so follow_hugetlb_page() which is called in get_dump_page() returns a wrong page from a given address. We need to filter out only hwpoison hugepages to have data on healthy hugepages in coredump. So this patch makes follow_hugetlb_page() avoid trying to get page when a pmd is in swap entry like format. Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com> Cc: stable@...r.kernel.org --- mm/hugetlb.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git v3.9-rc3.orig/mm/hugetlb.c v3.9-rc3/mm/hugetlb.c index 0d1705b..8462e2c 100644 --- v3.9-rc3.orig/mm/hugetlb.c +++ v3.9-rc3/mm/hugetlb.c @@ -2968,7 +2968,8 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, * first, for the page indexing below to work. */ pte = huge_pte_offset(mm, vaddr & huge_page_mask(h)); - absent = !pte || huge_pte_none(huge_ptep_get(pte)); + absent = !pte || huge_pte_none(huge_ptep_get(pte)) || + is_swap_pte(huge_ptep_get(pte)); /* * When coredumping, it suits get_dump_page if we just return -- 1.7.11.7 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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