mm/compaction: cleanup on compaction_deferred

When CONFIG_COMPACTION is enabled, compaction_deferred() tries to
recalculate the deferred limit again, which isn't necessary.

When CONFIG_COMPACTION is disabled, compaction_deferred() should return
"true" or "false" since it has "bool" for its return value.

Signed-off-by: Gavin Shan <shangw@linux.vnet.ibm.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/compaction.h

@@ -58,7 +58,7 @@ static inline bool compaction_deferred(struct zone *zone, int order)
 	if (++zone->compact_considered > defer_limit)
 		zone->compact_considered = defer_limit;
 
-	return zone->compact_considered < (1UL << zone->compact_defer_shift);
+	return zone->compact_considered < defer_limit;
 }
 
 #else
@@ -85,7 +85,7 @@ static inline void defer_compaction(struct zone *zone, int order)
 
 static inline bool compaction_deferred(struct zone *zone, int order)
 {
-	return 1;
+	return true;
 }
 
 #endif /* CONFIG_COMPACTION */