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    SubjectRe: [patch 2/2] [PATCH] mm: Save soft-dirty bits on file pages
    On Wed, 31 Jul 2013 00:41:56 +0400 Cyrill Gorcunov <gorcunov@gmail.com> wrote:

    > +#define pte_to_pgoff(pte) \
    > + ((((pte).pte_low >> (PTE_FILE_SHIFT1)) \
    > + & ((1U << PTE_FILE_BITS1) - 1))) \
    > + + ((((pte).pte_low >> (PTE_FILE_SHIFT2)) \
    > + & ((1U << PTE_FILE_BITS2) - 1)) \
    > + << (PTE_FILE_BITS1)) \
    > + + ((((pte).pte_low >> (PTE_FILE_SHIFT3)) \
    > + & ((1U << PTE_FILE_BITS3) - 1)) \
    > + << (PTE_FILE_BITS1 + PTE_FILE_BITS2)) \
    > + + ((((pte).pte_low >> (PTE_FILE_SHIFT4))) \
    > + << (PTE_FILE_BITS1 + PTE_FILE_BITS2 + PTE_FILE_BITS3))
    > +
    > +#define pgoff_to_pte(off) \
    > + ((pte_t) { .pte_low = \
    > + ((((off)) & ((1U << PTE_FILE_BITS1) - 1)) << PTE_FILE_SHIFT1) \
    > + + ((((off) >> PTE_FILE_BITS1) \
    > + & ((1U << PTE_FILE_BITS2) - 1)) \
    > + << PTE_FILE_SHIFT2) \
    > + + ((((off) >> (PTE_FILE_BITS1 + PTE_FILE_BITS2)) \
    > + & ((1U << PTE_FILE_BITS3) - 1)) \
    > + << PTE_FILE_SHIFT3) \
    > + + ((((off) >> \
    > + (PTE_FILE_BITS1 + PTE_FILE_BITS2 + PTE_FILE_BITS3))) \
    > + << PTE_FILE_SHIFT4) \
    > + + _PAGE_FILE })

    Good god.

    I wonder if these can be turned into out-of-line functions in some form
    which humans can understand.

    or

    #define pte_to_pgoff(pte)
    frob(pte, PTE_FILE_SHIFT1, PTE_FILE_BITS1) +
    frob(PTE_FILE_SHIFT2, PTE_FILE_BITS2) +
    frob(PTE_FILE_SHIFT3, PTE_FILE_BITS3) +
    frob(PTE_FILE_SHIFT4, PTE_FILE_BITS1 + PTE_FILE_BITS2 + PTE_FILE_BITS3)




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