Re: Multiple null mounts with same parameters

[Mouse <mouse%Rodents-Montreal.ORG@localhost>]

>>     # mount -t null /src /dest
>>     # mount -t null /src /dest
>>     # mount -t null /src /dest

>> Does it make sense to prevent the user from creating a null mount
>> whose parameters match an existing null mount?

> I don't think it really does.

I concur.  If it broke something in a way that were fundamentally
unfixable, then you might have a point.  But as far as I can see the
most this breaks is human-layer expectations, so IMO it falls into
"Unix does not prevent you from doing stupid things because that would
also prevent you from doing clever things".

At the moment, I see no `clever thing', no particular use for this,
though -o union strikes me as something to think hard about if you
really want one.  But I don't see any need to make an exception to the
usually-consistent stacking filesystem rules for it, either.  At the
very least I would say that any such prohibition should (a) be
implemented entirely in userland and (b) have an option to override it.

More generally, I don't see what problem you're trying to fix here.
Indeed, I don't see any problem here, possibly excepting human-layer
confusion, and that only if the human in question doesn't understand
how filesystem stacking works in general.

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