On 04/03/2013 02:35 PM, Naoya Horiguchi wrote:
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. ChangeLog v3: - add comment about using is_swap_pte() Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> Reviewed-by: Michal Hocko <mhocko@xxxxxxx> Acked-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx
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