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    SubjectRe: [RFC][PATCH 2/3] pagemap: export KPF_THP
    On Tue, Dec 20, 2011 at 02:38:38AM +0800, Naoya Horiguchi wrote:
    > This flag shows that a given pages is a subpage of transparent hugepage.
    > It does not care about whether it is a head page or a tail page, because
    > it's clear from pfn of the target page which you should know when you read
    > /proc/kpageflags.

    OK, this is aligning with KPF_HUGE. For those who only care about
    head/tail pages, will the KPF_COMPOUND_HEAD/KPF_COMPOUND_TAIL flags be
    set automatically for thp? Which may be more convenient to test/filter
    than the page address.

    > Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>

    Reviewed-by: Wu Fengguang <fengguang.wu@intel.com>

    As you already discussed, the below #ifdef should be removed.
    In fact, kernel-page-flags.h is intended for direct inclusion by
    user space tools, so must not have any conditional defines.

    > --- 3.2-rc5.orig/include/linux/kernel-page-flags.h
    > +++ 3.2-rc5/include/linux/kernel-page-flags.h
    > @@ -31,6 +31,10 @@
    >
    > #define KPF_KSM 21
    >
    > +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
    > +#define KPF_THP 22
    > +#endif
    > +
    > /* kernel hacking assistances
    > * WARNING: subject to change, never rely on them!
    > */
    > --
    > 1.7.7.3


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