It's not very elegant, but the quick and dirty solution is to use sudo 
to allow certain users to run specific commands with a real uid of 
root.  You can say exactly what arguments the user has to use - the 
sudoers file is where this is configured.  Or you can make a script - 
which is probably better.  But said script should have no arguments, or 
as few as possible - because any complexity allows that user to attempt 
to exploit it to acheive root.  Such a script could trivially bring a 
specific LV online, writable by a specific user.  More complex 
requirement would be - more complex.

If LVM has more elegant features for this kind of thing, I'm all ears.

On Fri, Nov 16, 2018 at 8:43 AM, Christoph Pleger 
<christoph.pleger@cs.uni-dortmund.de> wrote:
>> Go back to the beginning and describe the original problem you are
>> trying to solve and the constraints you have and ask for advice about
>> ways to achieve it.
> 
> The beginning is that I want to create a user-specific logical volume 
> when a user logs in to a service that authenticates its users through 
> pam and that does not run as root.
> 
> Regards
>   Christoph
>