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    Subject[PATCHv9-rebased2 13/37] thp: support file pages in zap_huge_pmd()
    Date
    split_huge_pmd() for file mappings (and DAX too) is implemented by just
    clearing pmd entry as we can re-fill this area from page cache on pte
    level later.

    This means we don't need deposit page tables when file THP is mapped.
    Therefore we shouldn't try to withdraw a page table on zap_huge_pmd()
    file THP PMD.

    Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
    ---
    mm/huge_memory.c | 12 +++++++++---
    1 file changed, 9 insertions(+), 3 deletions(-)

    diff --git a/mm/huge_memory.c b/mm/huge_memory.c
    index b24b7993c369..d8fd49073280 100644
    --- a/mm/huge_memory.c
    +++ b/mm/huge_memory.c
    @@ -1693,10 +1693,16 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
    struct page *page = pmd_page(orig_pmd);
    page_remove_rmap(page, true);
    VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
    - add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
    VM_BUG_ON_PAGE(!PageHead(page), page);
    - pte_free(tlb->mm, pgtable_trans_huge_withdraw(tlb->mm, pmd));
    - atomic_long_dec(&tlb->mm->nr_ptes);
    + if (PageAnon(page)) {
    + pgtable_t pgtable;
    + pgtable = pgtable_trans_huge_withdraw(tlb->mm, pmd);
    + pte_free(tlb->mm, pgtable);
    + atomic_long_dec(&tlb->mm->nr_ptes);
    + add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
    + } else {
    + add_mm_counter(tlb->mm, MM_FILEPAGES, -HPAGE_PMD_NR);
    + }
    spin_unlock(ptl);
    tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
    }
    --
    2.8.1
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