userfaultfd: wp: add pmd_swp_*uffd_wp() helpers

Adding these missing helpers for uffd-wp operations with pmd
swap/migration entries.

Signed-off-by: Peter Xu <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Reviewed-by: Jerome Glisse <[e-mail]>
Reviewed-by: Mike Rapoport <[e-mail]>
Cc: Andrea Arcangeli <[e-mail]>
Cc: Bobby Powers <[e-mail]>
Cc: Brian Geffon <[e-mail]>
Cc: David Hildenbrand <[e-mail]>
Cc: Denis Plotnikov <[e-mail]>
Cc: "Dr . David Alan Gilbert" <[e-mail]>
Cc: Hugh Dickins <[e-mail]>
Cc: Johannes Weiner <[e-mail]>
Cc: "Kirill A . Shutemov" <[e-mail]>
Cc: Martin Cracauer <[e-mail]>
Cc: Marty McFadden <[e-mail]>
Cc: Maya Gokhale <[e-mail]>
Cc: Mel Gorman <[e-mail]>
Cc: Mike Kravetz <[e-mail]>
Cc: Pavel Emelyanov <[e-mail]>
Cc: Rik van Riel <[e-mail]>
Cc: Shaohua Li <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Linus Torvalds <[e-mail]>

arch/x86/include/asm/pgtable.h

···
 {
 	return pte_clear_flags(pte, _PAGE_SWP_UFFD_WP);
 }
+
+static inline pmd_t pmd_swp_mkuffd_wp(pmd_t pmd)
+{
+	return pmd_set_flags(pmd, _PAGE_SWP_UFFD_WP);
+}
+
+static inline int pmd_swp_uffd_wp(pmd_t pmd)
+{
+	return pmd_flags(pmd) & _PAGE_SWP_UFFD_WP;
+}
+
+static inline pmd_t pmd_swp_clear_uffd_wp(pmd_t pmd)
+{
+	return pmd_clear_flags(pmd, _PAGE_SWP_UFFD_WP);
+}
 #endif /* CONFIG_HAVE_ARCH_USERFAULTFD_WP */
 
 #define PKRU_AD_BIT 0x1

include/asm-generic/pgtable_uffd.h

···
 {
 	return pte;
 }
+
+static inline pmd_t pmd_swp_mkuffd_wp(pmd_t pmd)
+{
+	return pmd;
+}
+
+static inline int pmd_swp_uffd_wp(pmd_t pmd)
+{
+	return 0;
+}
+
+static inline pmd_t pmd_swp_clear_uffd_wp(pmd_t pmd)
+{
+	return pmd;
+}
 #endif /* CONFIG_HAVE_ARCH_USERFAULTFD_WP */
 
 #endif /* _ASM_GENERIC_PGTABLE_UFFD_H */