enables the writing of page cache pages belonging to mst protected
      attributes like the index allocation attribute in directory indices
      and other indices like $Quota/$Q, etc.  This means that the quota is
      now marked out of date on all volumes rather than only on ones where
      the quota defaults entry is in the index root attribute of the
      $Quota/$Q index.
Signed-off-by: Anton Altaparmakov <aia21@cantab.net>