mm: use is_migrate_isolate_page() to simplify the code

Use is_migrate_isolate_page() to simplify the code, no functional
changes.

Link: http://lkml.kernel.org/r/58B94FB1.8020802@huawei.com
Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/page_isolation.c

@@ -88,7 +88,7 @@ static void unset_migratetype_isolate(struct page *page, unsigned migratetype)
 
 	zone = page_zone(page);
 	spin_lock_irqsave(&zone->lock, flags);
-	if (get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
+	if (!is_migrate_isolate_page(page))
 		goto out;
 
 	/*
@@ -205,7 +205,7 @@ int undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
 	     pfn < end_pfn;
 	     pfn += pageblock_nr_pages) {
 		page = __first_valid_page(pfn, pageblock_nr_pages);
-		if (!page || get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
+		if (!page || !is_migrate_isolate_page(page))
 			continue;
 		unset_migratetype_isolate(page, migratetype);
 	}
@@ -262,7 +262,7 @@ int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn,
 	 */
 	for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
 		page = __first_valid_page(pfn, pageblock_nr_pages);
-		if (page && get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
+		if (page && !is_migrate_isolate_page(page))
 			break;
 	}
 	page = __first_valid_page(start_pfn, end_pfn - start_pfn);