mm: do_migrate_range: reduce list_empty() check

Simple code for reducing list_empty(&source) check.
Signed-off-by: Bob Liu <lliubbo@gmail.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Wu Fengguang <fengguang.wu@intel.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memory_hotplug.c

@@ -705,24 +705,21 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
 			   check this again here. */
 			if (page_count(page)) {
 				not_managed++;
+				ret = -EBUSY;
 				break;
 			}
 		}
 	}
-	ret = -EBUSY;
+	if (!list_empty(&source)) {
 		if (not_managed) {
-		if (!list_empty(&source))
 			putback_lru_pages(&source);
 			goto out;
 		}
-	ret = 0;
-	if (list_empty(&source))
-		goto out;
 		/* this function returns # of failed pages */
 		ret = migrate_pages(&source, hotremove_migrate_alloc, 0, 1);
 		if (ret)
 			putback_lru_pages(&source);
-
+	}
 out:
 	return ret;
 }