f2fs: avoid needless lock for node pages when fsyncing a file

When fsync is called, sync_node_pages finds a proper direct node pages to flush.
But, it locks unrelated direct node pages together unnecessarily.
Acked-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/node.c

@@ -1272,10 +1272,14 @@ int sync_node_pages(struct f2fs_sb_info *sbi, nid_t ino,
 			 * we should not skip writing node pages.
 			 */
 lock_node:
-			if (ino && ino_of_node(page) == ino)
-				lock_page(page);
-			else if (!trylock_page(page))
+			if (ino) {
+				if (ino_of_node(page) == ino)
+					lock_page(page);
+				else
+					continue;
+			} else if (!trylock_page(page)) {
 				continue;
+			}
 
 			if (unlikely(page->mapping != NODE_MAPPING(sbi))) {
 continue_unlock: