<pseudocode>

    if dir !exists:
      mkdir && chown
    else:
      if dir has correct ownership:
        traverse
      else:
        // our code chowns correctly on create
        // so user must have done something
        // independently; better NOT mess with it
        throw "helpful descriptive message"

mkdirp creates OR traverses recursively based on whether each directory already exists or not. This is why correctMkdirp() is an insane idea: the "correct"-ing chown step should never be internal to mkdirp because it should never occur on traversal (i.e. when a pre-existing directory is encountered).