d_path and stackable filesystems

I'm trying to use d_path() inside a stackable filesystems (using fist), but it only figures out the path until the mount point of the stackable fs. Is this a limitation of the d_path algorithm, fist, both? any way of me working around it?

as far as I can tell it's because of this piece of code

      if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry) )  {
         /* Global root? */
       if (vfsmnt->mnt_parent == vfsmnt)
            goto global_root;

namely the vfsmnt->mnt_parent == vfsmnt.

any ideas on how I can work around it?

thanks,

shaya