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    SubjectRe: [PATCH] mm: make munlock fast when mlock is canceled by sigkill
    From
    > This patch is for making commit 4779280d1e (mm: make get_user_pages()
    > interruptible) complete.

    Yes.
    commit 4779280d1e (mm: make get_user_pages() interruptible) has never
    works as expected since it's born.
    IOW, it was totally broken.

    This patch is definitely good forward step patch.


    >> > @@ -254,6 +254,7 @@ static inline void
    >> > mminit_validate_memmodel_limits(unsigned long *start_pfn,
    >> >  #define GUP_FLAGS_FORCE                  0x2
    >> >  #define GUP_FLAGS_IGNORE_VMA_PERMISSIONS 0x4
    >> >  #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.
    >
    >  GUP_FLAGS_NOFAULT ?
    >
    > I wonder we can remove a hack of FOLL_ANON for core-dump by this flag, too.

    Yeah, GUP_FLAGS_NOFAULT is better.

    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?
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