You could also simply use non-intersecting cmd parameter values
for the new calls, which avaids the special flag, and leaves the
backward compatability without adding grundles of new system calls.
What about source-level compatibility, which IMO is a good thing,
at least if it doesn't add too much complexity (it clearly doesn't
in this case)? Also, handling single flag should be easier from
the coding perspective than a load of new values, after all
we can do something like: