kref: remove kref_set

Of the three uses of kref_set in the kernel:

 One really should be kref_put as the code is letting go of a
    reference,
 Two really should be kref_init because the kref is being
    initialised.

This suggests that making kref_set available encourages bad code.
So fix the three uses and remove kref_set completely.

Signed-off-by: NeilBrown <neilb@suse.de>
Acked-by: Mimi Zohar <zohar@us.ibm.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 076c7c8..b2d70d3 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -54,8 +54,8 @@
 #endif
 	/* tgcred will be cleared in our caller bc CLONE_THREAD won't be set */
 
-	/* alloc_uid() incremented the userns refcount.  Just set it to 1 */
-	kref_set(&ns->kref, 1);
+	/* root_user holds a reference to ns, our reference can be dropped */
+	put_user_ns(ns);
 
 	return 0;
 }