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    Subject[PATCH 3.8 085/166] mm: clear pmd_numa before invalidating
    Date
    3.8.13.16 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Mel Gorman <mgorman@suse.de>

    commit 67f87463d3a3362424efcbe8b40e4772fd34fc61 upstream.

    On x86, PMD entries are similar to _PAGE_PROTNONE protection and are
    handled as NUMA hinting faults. The following two page table protection
    bits are what defines them

    _PAGE_NUMA:set _PAGE_PRESENT:clear

    A PMD is considered present if any of the _PAGE_PRESENT, _PAGE_PROTNONE,
    _PAGE_PSE or _PAGE_NUMA bits are set. If pmdp_invalidate encounters a
    pmd_numa, it clears the present bit leaving _PAGE_NUMA which will be
    considered not present by the CPU but present by pmd_present. The
    existing caller of pmdp_invalidate should handle it but it's an
    inconsistent state for a PMD. This patch keeps the state consistent
    when calling pmdp_invalidate.

    Signed-off-by: Mel Gorman <mgorman@suse.de>
    Reviewed-by: Rik van Riel <riel@redhat.com>
    Cc: Alex Thorlton <athorlton@sgi.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Kamal Mostafa <kamal@canonical.com>
    ---
    mm/pgtable-generic.c | 3 +++
    1 file changed, 3 insertions(+)

    diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c
    index 0c8323f..eb900bb 100644
    --- a/mm/pgtable-generic.c
    +++ b/mm/pgtable-generic.c
    @@ -166,6 +166,9 @@ pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm)
    void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
    pmd_t *pmdp)
    {
    + pmd_t entry = *pmdp;
    + if (pmd_numa(entry))
    + entry = pmd_mknonnuma(entry);
    set_pmd_at(vma->vm_mm, address, pmdp, pmd_mknotpresent(*pmdp));
    flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
    }
    --
    1.8.3.2


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