f2fs: fix to report error in f2fs_readdir

get_lock_data_page in f2fs_readdir can fail due to a lot of reasons (i.e.
no memory or IO error...), it's better to report this kind of error to
user rather than ignoring it.
Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/dir.c

@@ -855,8 +855,13 @@ static int f2fs_readdir(struct file *file, struct dir_context *ctx)
 
 	for (; n < npages; n++) {
 		dentry_page = get_lock_data_page(inode, n, false);
-		if (IS_ERR(dentry_page))
+		if (IS_ERR(dentry_page)) {
+			err = PTR_ERR(dentry_page);
+			if (err == -ENOENT)
 				continue;
+			else
+				goto out;
+		}
 
 		dentry_blk = kmap(dentry_page);