Re: Add a mountlist iterator (round 2)

["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:
> 
>> 
>> On 5. Apr 2017, at 05:14, Chuck Silvers <chuq%chuq.com@localhost> wrote:
>> 
>> have you considered a callback-based interface where the loop
>> is inside the iteration API rather than in the caller?
>> the vfs_busy/unbusy could also be hidden in the iteration API
>> so that the callback would not need need to worry about it at all.
>> 
>> I looked at how the iteration stuff is used in your patches
>> (the first one, I haven't looked in the latest one in detail)
>> and it looks like most of users would be fine with not being able
>> to do anything after vfs_unbusy().  the one place that really does
>> want to do more after vfs_unbusy() is vfs_unmountall1(),
>> but that could be rewritten to loop unmounting the last mount
>> in the list until they're all gone.
>> 
>> I think this would further simplify most (if not all) cases of
>> mountlist iteration.
> 
> Good hint.  Prepared a partial implementation of
> 
> int
> mountlist_iterate(int (*cb)(struct mount *, void *), void *arg)
> 
> to take "mp" busy and call "cb(mp, arg)" for all mounted file systems.
> 
> A non waiting variant "mountlist_iterate_nowait()" could be added
> when it gets needed.
> 
> Changed "vfs_unmountall1()" to retrieve mounts in descending
> generation order which has the additional benefit that we don't
> need reverse traversals any more.
> 
> 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.

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