f2fs: read with READ_SYNC when getting dnode page

The get_node_page_ra tries to:
1. grab or read a target node page for the given nid,
2. then, call ra_node_page to read other adjacent node pages in advance.

So, when we try to read a target node page by #1, we should submit bio with
READ_SYNC instead of READA.
And, in #2, READA should be used.
Signed-off-by: NJaegeuk Kim <jaegeuk.kim@samsung.com>
Reviewed-by: NNamjae Jeon <namjae.jeon@samsung.com>

fs/f2fs/node.c

@@ -930,7 +930,7 @@ struct page *get_node_page_ra(struct page *parent, int start)
 	if (!page)
 		return ERR_PTR(-ENOMEM);
 
-	err = read_node_page(page, READA);
+	err = read_node_page(page, READ_SYNC);
 	if (err) {
 		f2fs_put_page(page, 1);
 		return ERR_PTR(err);