From: Arvind Kandhare <arvind.kan@wipro.com>

When switch_uid is called, the reference count of the new user is
incremented twice.  I think the increment in the switch_uid is done because
of the reparent_to_init() function which does not increase the __count for
root user.

But if switch_uid is called from any other function, the reference count is
already incremented by the caller by calling alloc_uid for the new user.
Hence the count is incremented twice.  The user struct will not be deleted
even when there are no processes holding a reference count for it.  This
does not cause any problem currently because nothing is dependent on timely
deletion of the user struct.