[PATCH v2 1/2] mm/page_alloc: remove unnecessary check in break_down_buddy_pages

[PATCH v2 1/2] mm/page_alloc: remove unnecessary check in break_down_buddy_pages

[Kemeng Shi]

1. We always have target in range started with next_page and full free
range started with current_buddy.
2. The last split range size is 1 << low and low should be >= 0, then
size >= 1. So page + size != page is always true (because size > 0).
As summary, current_page will not equal to target page.

Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
---
 mm/page_alloc.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e18e0e20eff8..bad979493dde 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6696,10 +6696,8 @@ static void break_down_buddy_pages(struct zone *zone, struct page *page,
 		if (set_page_guard(zone, current_buddy, high, migratetype))
 			continue;
 
-		if (current_buddy != target) {
-			add_to_free_list(current_buddy, zone, high, migratetype);
-			set_buddy_order(current_buddy, high);
-		}
+		add_to_free_list(current_buddy, zone, high, migratetype);
+		set_buddy_order(current_buddy, high);
 	}
 }
 
-- 
2.30.0

[PATCH v2 2/2] mm/page_alloc: remove unnecessary next_page in break_down_buddy_pages

[Kemeng Shi]

The next_page is only used to forward page in case target is in second
half range. Move forward page directly to remove unnecessary next_page.

Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
---
 mm/page_alloc.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index bad979493dde..7df77b58a961 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6678,20 +6678,18 @@ static void break_down_buddy_pages(struct zone *zone, struct page *page,
 				   int migratetype)
 {
 	unsigned long size = 1 << high;
-	struct page *current_buddy, *next_page;
+	struct page *current_buddy;
 
 	while (high > low) {
 		high--;
 		size >>= 1;
 
 		if (target >= &page[size]) {
-			next_page = page + size;
 			current_buddy = page;
+			page = page + size;
 		} else {
-			next_page = page;
 			current_buddy = page + size;
 		}
-		page = next_page;
 
 		if (set_page_guard(zone, current_buddy, high, migratetype))
 			continue;
-- 
2.30.0