mm: use zone_is_empty() instead of if(zone->spanned_pages)

Use "zone_is_empty()" instead of "if (zone->spanned_pages)".
Simplify the code, no functional change.

Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
Cc: Cody P Schafer <cody@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memory_hotplug.c

@@ -230,7 +230,7 @@ static void grow_zone_span(struct zone *zone, unsigned long start_pfn,
 	zone_span_writelock(zone);
 
 	old_zone_end_pfn = zone_end_pfn(zone);
-	if (!zone->spanned_pages || start_pfn < zone->zone_start_pfn)
+	if (zone_is_empty(zone) || start_pfn < zone->zone_start_pfn)
 		zone->zone_start_pfn = start_pfn;
 
 	zone->spanned_pages = max(old_zone_end_pfn, end_pfn) -
@@ -305,7 +305,7 @@ static int __meminit move_pfn_range_left(struct zone *z1, struct zone *z2,
 		goto out_fail;
 
 	/* use start_pfn for z1's start_pfn if z1 is empty */
-	if (z1->spanned_pages)
+	if (!zone_is_empty(z1))
 		z1_start_pfn = z1->zone_start_pfn;
 	else
 		z1_start_pfn = start_pfn;
@@ -347,7 +347,7 @@ static int __meminit move_pfn_range_right(struct zone *z1, struct zone *z2,
 		goto out_fail;
 
 	/* use end_pfn for z2's end_pfn if z2 is empty */
-	if (z2->spanned_pages)
+	if (!zone_is_empty(z2))
 		z2_end_pfn = zone_end_pfn(z2);
 	else
 		z2_end_pfn = end_pfn;

mm/page_alloc.c

@@ -1306,7 +1306,7 @@ void mark_free_pages(struct zone *zone)
 	int order, t;
 	struct list_head *curr;
 
-	if (!zone->spanned_pages)
+	if (zone_is_empty(zone))
 		return;
 
 	spin_lock_irqsave(&zone->lock, flags);