powerpc/mm: Implement _PAGE_SPECIAL & pte_special() for 64-bit

Implement _PAGE_SPECIAL and pte_special() for 64-bit powerpc. This bit will
be used by the fast get_user_pages() to differenciate PTEs that correspond
to a valid struct page from special mappings that don't such as IO mappings
obtained via io_remap_pfn_ranges().

Signed-off-by: Nick Piggin <[e-mail]>
Acked-by: Benjamin Herrenschmidt <[e-mail]>
Cc: Paul Mackerras <[e-mail]>
Cc: Hugh Dickins <[e-mail]>
Cc: "Paul E. McKenney" <[e-mail]>
Reviewed-by: Peter Zijlstra <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Benjamin Herrenschmidt <[e-mail]>

include/asm-powerpc/pgtable-4k.h

···
 #define _PAGE_GROUP_IX  0x7000 /* software: HPTE index within group */
 #define _PAGE_F_SECOND  _PAGE_SECONDARY
 #define _PAGE_F_GIX     _PAGE_GROUP_IX
+#define _PAGE_SPECIAL	0x10000 /* software: special page */
+#define __HAVE_ARCH_PTE_SPECIAL
 
 /* PTE flags to conserve for HPTE identification */
 #define _PAGE_HPTEFLAGS (_PAGE_BUSY | _PAGE_HASHPTE | \

include/asm-powerpc/pgtable-64k.h

···
 #define PGDIR_MASK	(~(PGDIR_SIZE-1))
 
 /* Additional PTE bits (don't change without checking asm in hash_low.S) */
+#define __HAVE_ARCH_PTE_SPECIAL
+#define _PAGE_SPECIAL	0x00000400 /* software: special page */
 #define _PAGE_HPTE_SUB	0x0ffff000 /* combo only: sub pages HPTE bits */
 #define _PAGE_HPTE_SUB0	0x08000000 /* combo only: first sub page */
 #define _PAGE_COMBO	0x10000000 /* this is a combo 4k page */

include/asm-powerpc/pgtable-ppc64.h

···
 static inline int pte_dirty(pte_t pte) { return pte_val(pte) & _PAGE_DIRTY;}
 static inline int pte_young(pte_t pte) { return pte_val(pte) & _PAGE_ACCESSED;}
 static inline int pte_file(pte_t pte) { return pte_val(pte) & _PAGE_FILE;}
-static inline int pte_special(pte_t pte) { return 0; }
+static inline int pte_special(pte_t pte) { return pte_val(pte) & _PAGE_SPECIAL; }
 
 static inline void pte_uncache(pte_t pte) { pte_val(pte) |= _PAGE_NO_CACHE; }
 static inline void pte_cache(pte_t pte)   { pte_val(pte) &= ~_PAGE_NO_CACHE; }
···
 static inline pte_t pte_mkhuge(pte_t pte) {
 	return pte; }
 static inline pte_t pte_mkspecial(pte_t pte) {
-	return pte; }
+	pte_val(pte) |= _PAGE_SPECIAL; return pte; }
 static inline unsigned long pte_pgprot(pte_t pte)
 {
 	return __pgprot(pte_val(pte)) & PAGE_PROT_BITS;