code: private void downgradeEdge(int edgeEntryIndex) {
      EdgeEntry entry = (EdgeEntry) mEntries.get(edgeEntryIndex);
      LockResource lock = mInodeLockManager.lockEdge(entry.mEdge, LockMode.READ);
      entry.getLock().close();
      mEntries.set(edgeEntryIndex, new EdgeEntry(lock, entry.getEdge()));
    }
docs: Downgrades the edge at the specified entry index.