mm/compaction.c: fix "suitable_migration_target() unused" warning

mm/compaction.c:250:13: warning: 'suitable_migration_target' defined but not used [-Wunused-function]
Reported-by: NFengguang Wu <fengguang.wu@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/compaction.c

@@ -391,28 +391,6 @@ static inline bool compact_should_abort(struct compact_control *cc)
 	return false;
 }
 
-/* Returns true if the page is within a block suitable for migration to */
-static bool suitable_migration_target(struct page *page)
-{
-	/* If the page is a large free page, then disallow migration */
-	if (PageBuddy(page)) {
-		/*
-		 * We are checking page_order without zone->lock taken. But
-		 * the only small danger is that we skip a potentially suitable
-		 * pageblock, so it's not worth to check order for valid range.
-		 */
-		if (page_order_unsafe(page) >= pageblock_order)
-			return false;
-	}
-
-	/* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */
-	if (migrate_async_suitable(get_pageblock_migratetype(page)))
-		return true;
-
-	/* Otherwise skip the block */
-	return false;
-}
-
 /*
  * Isolate free pages onto a private freelist. If @strict is true, will abort
  * returning 0 on any invalid PFNs or non-free pages inside of the pageblock
@@ -896,6 +874,29 @@ isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn,
 
 #endif /* CONFIG_COMPACTION || CONFIG_CMA */
 #ifdef CONFIG_COMPACTION
+
+/* Returns true if the page is within a block suitable for migration to */
+static bool suitable_migration_target(struct page *page)
+{
+	/* If the page is a large free page, then disallow migration */
+	if (PageBuddy(page)) {
+		/*
+		 * We are checking page_order without zone->lock taken. But
+		 * the only small danger is that we skip a potentially suitable
+		 * pageblock, so it's not worth to check order for valid range.
+		 */
+		if (page_order_unsafe(page) >= pageblock_order)
+			return false;
+	}
+
+	/* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */
+	if (migrate_async_suitable(get_pageblock_migratetype(page)))
+		return true;
+
+	/* Otherwise skip the block */
+	return false;
+}
+
 /*
  * Based on information in the current compact_control, find blocks
  * suitable for isolating free pages from and then isolate them.