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    Subject[PATCH v3 08/14] mm/gup: Break COW PTE in follow_pfn_pte()
    Date
    In most of cases, GUP will not modify the page table,
    excluding follow_pfn_pte(). To deal with COW PTE, break
    COW PTE in follow_pfn_pte().

    Signed-off-by: Chih-En Lin <shiyn.lin@gmail.com>
    ---
    mm/gup.c | 2 ++
    1 file changed, 2 insertions(+)

    diff --git a/mm/gup.c b/mm/gup.c
    index fe195d47de74a..cd72010ba0e6d 100644
    --- a/mm/gup.c
    +++ b/mm/gup.c
    @@ -476,6 +476,8 @@ static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address,
    entry = pte_mkyoung(entry);

    if (!pte_same(*pte, entry)) {
    + if (break_cow_pte(vma, NULL, address) < 0)
    + return -ENOMEM;
    set_pte_at(vma->vm_mm, address, pte, entry);
    update_mmu_cache(vma, address, pte);
    }
    --
    2.37.3
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