Messages in this thread Patch in this message | | | From | Naoya Horiguchi <> | Subject | [PATCH 2/2] hugetlbfs: add swap entry check in follow_hugetlb_page() | Date | Thu, 28 Mar 2013 11:42:38 -0400 |
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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@ah.jp.nec.com> --- 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
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