mm/page_alloc: remove unnecessary next_page in break_down_buddy_pages

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.

Link: https://lkml.kernel.org/r/20230927103514.98281-3-shikemeng@huaweicloud.comSigned-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/page_alloc.c

@@ -6462,20 +6462,18 @@ 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;