cifs: update ctime and mtime during truncate

As the man description of the truncate, if the size changed,
then the st_ctime and st_mtime fields should be updated. But
in cifs, we doesn't do it.

It lead the xfstests generic/313 failed.

So, add the ATTR_MTIME|ATTR_CTIME flags on attrs when change
the file size
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zhang Xiaoxu <zhangxiaoxu5@huawei.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/inode.c

@@ -2535,6 +2535,15 @@ cifs_set_file_size(struct inode *inode, struct iattr *attrs,
 	if (rc == 0) {
 		cifsInode->server_eof = attrs->ia_size;
 		cifs_setsize(inode, attrs->ia_size);
+
+		/*
+		 * The man page of truncate says if the size changed,
+		 * then the st_ctime and st_mtime fields for the file
+		 * are updated.
+		 */
+		attrs->ia_ctime = attrs->ia_mtime = current_time(inode);
+		attrs->ia_valid |= ATTR_CTIME | ATTR_MTIME;
+
 		cifs_truncate_page(inode->i_mapping, inode->i_size);
 	}