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    Subject[PATCH v3 05/10] thp: change_huge_pmd(): keep huge zero page write-protected
    Date
    From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>

    We want to get page fault on write attempt to huge zero page, so let's
    keep it write-protected.

    Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
    Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
    ---
    mm/huge_memory.c | 2 ++
    1 files changed, 2 insertions(+), 0 deletions(-)

    diff --git a/mm/huge_memory.c b/mm/huge_memory.c
    index f30f39d..d864cd4 100644
    --- a/mm/huge_memory.c
    +++ b/mm/huge_memory.c
    @@ -1249,6 +1249,8 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
    pmd_t entry;
    entry = pmdp_get_and_clear(mm, addr, pmd);
    entry = pmd_modify(entry, newprot);
    + if (is_huge_zero_pmd(entry))
    + entry = pmd_wrprotect(entry);
    set_pmd_at(mm, addr, pmd, entry);
    spin_unlock(&vma->vm_mm->page_table_lock);
    ret = 1;
    --
    1.7.7.6


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