[OpenAFS] user-visible change suggestion for fs setacl

[Felix Frank]

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On Wed, 17 Dec 2008, Erik Dal=E9n wrote:

> On Wed, Dec 17, 2008 at 03:09, Stephen Joyce <stephen@physics.unc.edu> =
wrote:
>> On Tue, 16 Dec 2008, Tom Maher wrote:
>>
>>> What's the semantics for negative ACLs?  For example,
>>>
>>> fs sa . system:authuser rl
>>> fs sa . badguy +rl -negative
>>>
>>> I'm guessing that'll give badguy negative "rl" bits.
>>
>> Makes sense to me.
>>
>>> Should 'fs sa . badguy -rl' implicitly give him negative "rl" bits, i=
f
>>> he doesn't have anything already?
>>
>> That doesn't make sense to me. I'd suggest that -<perm> should never a=
dd
>> permissions, only remove. So it should just clear the perms if they're=
 set
>> and do nothing if not. To add the negative flags, do what you suggeste=
d
>> above.
>>
>> My $0.02.
>
> Sounds very reasonable to me. My vote for implementing it like this.

Still doesn't feel devoid of ambiguity, though:

fs sa . user +rl -negative	# sets negative bits
fs sa . user -rl -negative	# takes away negative bits?
fs sa . user -rl		# takes away both negative and positive bits?
 				# or positive only? what about neg. then?

To add more confusion, I find another model conceivable:

fs sa . user +a         # always removes negative bit, adds positive bit
fs sa . user -a         # always sets negative bit, removes positive bit

the drawbacks being painfully obvious.

In all, with ACLs having one degree of higher complexity than unix=20
permissions, there probably is no way to make this syntax 100% intuitivel=
y=20
akin to chmod's.
Thus, the original proposal to use postfix +/- might communicate the
distinction?

Regards
Felix
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