mm: workingset: #define radix entry eviction mask

This is a compile-time constant, no need to calculate it on refault.
Signed-off-by: NJohannes Weiner <hannes@cmpxchg.org>
Reviewed-by: NVladimir Davydov <vdavydov@virtuozzo.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/workingset.c

@@ -152,6 +152,10 @@
  * refault distance will immediately activate the refaulting page.
  */
 
+#define EVICTION_SHIFT	(RADIX_TREE_EXCEPTIONAL_ENTRY + \
+			 ZONES_SHIFT + NODES_SHIFT)
+#define EVICTION_MASK	(~0UL >> EVICTION_SHIFT)
+
 static void *pack_shadow(unsigned long eviction, struct zone *zone)
 {
 	eviction = (eviction << NODES_SHIFT) | zone_to_nid(zone);
@@ -168,7 +172,6 @@ static void unpack_shadow(void *shadow,
 	unsigned long entry = (unsigned long)shadow;
 	unsigned long eviction;
 	unsigned long refault;
-	unsigned long mask;
 	int zid, nid;
 
 	entry >>= RADIX_TREE_EXCEPTIONAL_SHIFT;
@@ -181,8 +184,7 @@ static void unpack_shadow(void *shadow,
 	*zone = NODE_DATA(nid)->node_zones + zid;
 
 	refault = atomic_long_read(&(*zone)->inactive_age);
-	mask = ~0UL >> (NODES_SHIFT + ZONES_SHIFT +
-			RADIX_TREE_EXCEPTIONAL_SHIFT);
+
 	/*
 	 * The unsigned subtraction here gives an accurate distance
 	 * across inactive_age overflows in most cases.
@@ -199,7 +201,7 @@ static void unpack_shadow(void *shadow,
 	 * inappropriate activation leading to pressure on the active
 	 * list is not a problem.
 	 */
-	*distance = (refault - eviction) & mask;
+	*distance = (refault - eviction) & EVICTION_MASK;
 }
 
 /**