x86: mm: restore original pte_special check

Commit b38af47 ("x86,mm: fix pte_special versus pte_numa") adjusted
the pte_special check to take into account that a special pte had
SPECIAL and neither PRESENT nor PROTNONE.  Now that NUMA hinting PTEs
are no longer modifying _PAGE_PRESENT it should be safe to restore the
original pte_special behaviour.

Signed-off-by: Mel Gorman <[email protected]>
Cc: Aneesh Kumar K.V <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Dave Jones <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Kirill Shutemov <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Sasha Levin <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: Mel Gorman

arch/x86/include/asm/pgtable.h

@@ -132,13 +132,7 @@ static inline int pte_exec(pte_t pte)
 
 static inline int pte_special(pte_t pte)
 {
-	/*
-	 * See CONFIG_NUMA_BALANCING pte_numa in include/asm-generic/pgtable.h.
-	 * On x86 we have _PAGE_BIT_NUMA == _PAGE_BIT_GLOBAL+1 ==
-	 * __PAGE_BIT_SOFTW1 == _PAGE_BIT_SPECIAL.
-	 */
-	return (pte_flags(pte) & _PAGE_SPECIAL) &&
-		(pte_flags(pte) & (_PAGE_PRESENT|_PAGE_PROTNONE));
+	return pte_flags(pte) & _PAGE_SPECIAL;
 }
 
 static inline unsigned long pte_pfn(pte_t pte)