[PATCH v2] mm/page_alloc: simplify page_is_buddy() for better code readability

[qiwuchen55@gmail.com]

From: chenqiwu <chenqiwu@xiaomi.com>

Simplify page_is_buddy() to reduce the redundant code for better code
readability.

Signed-off-by: chenqiwu <chenqiwu@xiaomi.com>
---
changes in v2:
 - split the conditional statement into four separate tests
   for better code readability.
---
 mm/page_alloc.c | 32 +++++++++++++-------------------
 1 file changed, 13 insertions(+), 19 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 3c4eb75..b221f6d 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -794,29 +794,23 @@ static inline void set_page_order(struct page *page, unsigned int order)
 static inline int page_is_buddy(struct page *page, struct page *buddy,
 							unsigned int order)
 {
-	if (page_is_guard(buddy) && page_order(buddy) == order) {
-		if (page_zone_id(page) != page_zone_id(buddy))
-			return 0;
-
-		VM_BUG_ON_PAGE(page_count(buddy) != 0, buddy);
+	if (page_order(buddy) != order)
+		return 0;
 
-		return 1;
-	}
+	if (!page_is_guard(buddy) && !PageBuddy(buddy))
+		return 0;
 
-	if (PageBuddy(buddy) && page_order(buddy) == order) {
-		/*
-		 * zone check is done late to avoid uselessly
-		 * calculating zone/node ids for pages that could
-		 * never merge.
-		 */
-		if (page_zone_id(page) != page_zone_id(buddy))
-			return 0;
+	/*
+	 * zone check is done late to avoid uselessly
+	 * calculating zone/node ids for pages that could
+	 * never merge.
+	 */
+	if (page_zone_id(page) != page_zone_id(buddy))
+		return 0;
 
-		VM_BUG_ON_PAGE(page_count(buddy) != 0, buddy);
+	VM_BUG_ON_PAGE(page_count(buddy) != 0, buddy);
 
-		return 1;
-	}
-	return 0;
+	return 1;
 }
 
 #ifdef CONFIG_COMPACTION
-- 
1.9.1