OK, so at this point svc_close_net(serv, current->nsproxy->net_ns) is
enough to clear out sv_permsocks and sv_temp_socks because we know that
the only sockets left are in that namespace. Got it.
I'm not sure. The one thing that might have helped mere here would be
a comment to explain what's going on, maybe something like:
svc_close_net(serv, net);
+ /*
+ * The last user is gone, so the only sockets left belonged its
+ * network namespace:
+ */
BUG_ON(!list_empty(&serv->sv_permsocks));
BUG_ON(!list_empty(&serv->sv_tempsocks));