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-horigu...@ah.jp.nec.com>
Reviewed-by: Michal Hocko <mho...@suse.cz>
Acked-by: Konstantin Khlebnikov <khlebni...@openvz.org>
Cc: sta...@vger.kernel.org
Reviewed-by: Rik van Riel <r...@redhat.com>
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