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    SubjectRe: [PATCH] mm: make munlock fast when mlock is canceled by sigkill
    Thank you for reviews.

    >>> > @@ -254,6 +254,7 @@ static inline void
    >>> > mminit_validate_memmodel_limits(unsigned long *start_pfn,
    >>> >  #define GUP_FLAGS_FORCE                  0x2
    >>> >  #define GUP_FLAGS_IGNORE_SIGKILL         0x8
    >>> > +#define GUP_FLAGS_ALLOW_NULL             0x10
    >>> >
    >>> I am worried about adding new flag whenever we need it.
    >>> But I think this case makes sense to me.
    >>> In addition, I guess ZERO page can also use this flag.
    >>> Kame. What do you think about it?
    >> I do welcome this !
    >> Then, I don't have to take care of mlock/munlock in ZERO_PAGE patch.
    >> And without this patch, munlock() does copy-on-write just for unpinning memory.
    >> So, this patch shows some right direction, I think.
    >> One concern is flag name, ALLOW_NULL sounds not very good.
    >> I wonder we can remove a hack of FOLL_ANON for core-dump by this flag, too.
    > Yeah, GUP_FLAGS_NOFAULT is better.

    Me too.
    I will change this flag name.

    > Plus, this patch change __get_user_pages() return value meaning IOW.
    > after this patch, it can return following value,
    >  return value: 3
    >  pages[0]: hoge-page
    >  pages[1]: null
    >  pages[2]: fuga-page
    > but, it can be
    >  return value: 2
    >  pages[0]: hoge-page
    >  pages[1]: fuga-page
    > no?

    I did misunderstand mean of get_user_pages()'s return value.

    When I try to change __get_user_pages(), I got problem.
    If remove NULLs from pages,
    __mlock_vma_pages_range() cannot know how long __get_user_pages() readed.
    So, I have to get the virtual address of the page from vma and page.
    Because __mlock_vma_pages_range() have to call
    __get_user_pages() many times with different `start' argument.

    I try to use page_address_in_vma(), but it failed.
    (page_address_in_vma() returned -EFAULT)
    I cannot find way to solve this problem.
    Are there good ideas?
    Please give me some ideas.

    Hiroaki Wakabayashi
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      Last update: 2009-08-25 06:49    [W:0.024 / U:11.784 seconds]
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