ovl_has_upperdata
if (ovl_has_upperdata(inode))
bool ovl_has_upperdata(struct inode *inode);
ovl_has_upperdata(d_inode(dentry))))
if (!ovl_has_upperdata(d_inode(dentry)))
!ovl_has_upperdata(d_inode(dentry)))
if (upperinode && ovl_has_upperdata(inode))
return !ovl_has_upperdata(d_inode(dentry));