mm/swapfile: use list_{prev,next}_entry() instead of open-coding

Use list_{prev,next}_entry() instead of list_entry() for better
code readability.

Signed-off-by: chenqiwu <chenqiwu@xiaomi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Yang Shi <yang.shi@linux.alibaba.com>
Cc: Qian Cai <cai@lca.pw>
Cc: Baoquan He <bhe@redhat.com>
Link: http://lkml.kernel.org/r/1586599916-15456-2-git-send-email-qiwuchen55@gmail.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/swapfile.c

@@ -3654,7 +3654,7 @@ static bool swap_count_continued(struct swap_info_struct *si,
 
 	spin_lock(&si->cont_lock);
 	offset &= ~PAGE_MASK;
-	page = list_entry(head->lru.next, struct page, lru);
+	page = list_next_entry(head, lru);
 	map = kmap_atomic(page) + offset;
 
 	if (count == SWAP_MAP_MAX)	/* initial increment from swap_map */
@@ -3666,13 +3666,13 @@ static bool swap_count_continued(struct swap_info_struct *si,
 		 */
 		while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) {
 			kunmap_atomic(map);
-			page = list_entry(page->lru.next, struct page, lru);
+			page = list_next_entry(page, lru);
 			BUG_ON(page == head);
 			map = kmap_atomic(page) + offset;
 		}
 		if (*map == SWAP_CONT_MAX) {
 			kunmap_atomic(map);
-			page = list_entry(page->lru.next, struct page, lru);
+			page = list_next_entry(page, lru);
 			if (page == head) {
 				ret = false;	/* add count continuation */
 				goto out;
@@ -3682,12 +3682,10 @@ init_map:		*map = 0;		/* we didn't zero the page */
 		}
 		*map += 1;
 		kunmap_atomic(map);
-		page = list_entry(page->lru.prev, struct page, lru);
-		while (page != head) {
+		while ((page = list_prev_entry(page, lru)) != head) {
 			map = kmap_atomic(page) + offset;
 			*map = COUNT_CONTINUED;
 			kunmap_atomic(map);
-			page = list_entry(page->lru.prev, struct page, lru);
 		}
 		ret = true;			/* incremented */
 
@@ -3698,7 +3696,7 @@ init_map:		*map = 0;		/* we didn't zero the page */
 		BUG_ON(count != COUNT_CONTINUED);
 		while (*map == COUNT_CONTINUED) {
 			kunmap_atomic(map);
-			page = list_entry(page->lru.next, struct page, lru);
+			page = list_next_entry(page, lru);
 			BUG_ON(page == head);
 			map = kmap_atomic(page) + offset;
 		}
@@ -3707,13 +3705,11 @@ init_map:		*map = 0;		/* we didn't zero the page */
 		if (*map == 0)
 			count = 0;
 		kunmap_atomic(map);
-		page = list_entry(page->lru.prev, struct page, lru);
-		while (page != head) {
+		while ((page = list_prev_entry(page, lru)) != head) {
 			map = kmap_atomic(page) + offset;
 			*map = SWAP_CONT_MAX | count;
 			count = COUNT_CONTINUED;
 			kunmap_atomic(map);
-			page = list_entry(page->lru.prev, struct page, lru);
 		}
 		ret = count == COUNT_CONTINUED;
 	}