Re: Add a mountlist iterator (round 2)

["J. Hannken-Illjes" <hannken%eis.cs.tu-bs.de@localhost>]

> On 9. Apr 2017, at 19:16, Taylor R Campbell <campbell+netbsd-tech-kern%mumble.net@localhost> wrote:
> 
>> Date: Sun, 9 Apr 2017 18:47:25 +0200
>> From: "J. Hannken-Illjes" <hannken%eis.cs.tu-bs.de@localhost>
>> 
>>> On 6. Apr 2017, at 11:44, J. Hannken-Illjes <hannken%eis.cs.tu-bs.de@localhost> wrote:
>>> Good hint.  Prepared a partial implementation of
>>> 
>>> int
>>> mountlist_iterate(int (*cb)(struct mount *, void *), void *arg)
>>> [...]
>>> Diffs are here: https://www.netbsd.org/~hannken/ml_iterator2a/
>>> 
>>> I prefer this API, opinions?
>> 
>> If no one objects I will commit this iterator on Tuesday, April 11.
> 
> I tend to prefer an iterator-style API over a callback-style API where
> it works.  (E.g., obviously xcall(9) can't be done with an iterator-
> style API.)  I like to avoid writing my code upside-down unless it's
> really necessary.  If you want a callback-style API for some reason,
> you can always write that in terms of an iterator-style API, but not
> vice versa.
> 
> Note the suggestion I made earlier about mountlist_iterator_next_done
> isn't necessary as long as anyone trying to break the loop and keep
> using the mount does something extra to acquire a reference:
> 
> mountlist_iterator_begin(&it);
> while ((mp = mountlist_iterator_next(&it)) != NULL) {
> 	dostuff(mp);
> 	if (interesting(mp)) {
> 		vfs_busy(mp);
> 		break;
> 	}
> }
> mountlist_iterator_end(&it);
> 
> All you have to do to make this work is store the last mp in the
> iterator too, so that mountlist_iterator_next can release it before
> acquiring the next one.
> 
> But I'm not the one doing the work here, so this is not an objection!

... and I am open to both approaches, I just want it done :-)

--
J. Hannken-Illjes - hannken%eis.cs.tu-bs.de@localhost - TU Braunschweig (Germany)