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    SubjectRe: [PATCH v6 04/23] mm/uffd: PTE_MARKER_UFFD_WP
    Date
    On Monday, 15 November 2021 6:55:03 PM AEDT Peter Xu wrote:

    [...]

    > +/*
    > + * Returns true if this is a swap pte and was uffd-wp wr-protected in either
    > + * forms (pte marker or a normal swap pte), false otherwise.
    > + */
    > +static inline bool pte_swp_uffd_wp_any(pte_t pte)
    > +{
    > +#ifdef CONFIG_PTE_MARKER_UFFD_WP
    > + if (!is_swap_pte(pte))
    > + return false;
    > +
    > + if (pte_swp_uffd_wp(pte))
    > + return true;

    If I'm not mistaken normal swap uffd-wp ptes can still exist when
    CONFIG_PTE_MARKER_UFFD_WP=n so shouldn't this be outside the #ifdef protection?

    In fact we could drop the #ifdef entirely here as it is safe to call
    is_pte_marker_uffd_wp() without CONFIG_PTE_MARKER_UFFD_WP.

    > +
    > + if (is_pte_marker_uffd_wp(pte))
    > + return true;
    > +#endif
    > + return false;
    > +}
    > +
    > #endif /* _LINUX_USERFAULTFD_K_H */
    > diff --git a/mm/Kconfig b/mm/Kconfig
    > index 66f23c6c2032..f01c8e0afadf 100644
    > --- a/mm/Kconfig
    > +++ b/mm/Kconfig
    > @@ -904,6 +904,15 @@ config PTE_MARKER
    > help
    > Allows to create marker PTEs for file-backed memory.
    >
    > +config PTE_MARKER_UFFD_WP
    > + bool "Marker PTEs support for userfaultfd write protection"
    > + depends on PTE_MARKER && HAVE_ARCH_USERFAULTFD_WP
    > +
    > + help
    > + Allows to create marker PTEs for userfaultfd write protection
    > + purposes. It is required to enable userfaultfd write protection on
    > + file-backed memory types like shmem and hugetlbfs.
    > +
    > source "mm/damon/Kconfig"
    >
    > endmenu
    >




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