nfsd4: nfsd_shutdown_net needs state lock

A comment claims the caller should take it, but that's not being done.
Note we don't want it around the cancel_delayed_work_sync since that may
wait on work which holds the client lock.
Reported-by: Benny Halevy <bhalevy@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/nfs4state.c

@@ -5124,7 +5124,6 @@ nfs4_state_start(void)
 	return ret;
 }
 
-/* should be called with the state lock held */
 void
 nfs4_state_shutdown_net(struct net *net)
 {
@@ -5135,6 +5134,7 @@ nfs4_state_shutdown_net(struct net *net)
 	cancel_delayed_work_sync(&nn->laundromat_work);
 	locks_end_grace(&nn->nfsd4_manager);
 
+	nfs4_lock_state();
 	INIT_LIST_HEAD(&reaplist);
 	spin_lock(&recall_lock);
 	list_for_each_safe(pos, next, &nn->del_recall_lru) {
@@ -5149,6 +5149,7 @@ nfs4_state_shutdown_net(struct net *net)
 
 	nfsd4_client_tracking_exit(net);
 	nfs4_state_destroy_net(net);
+	nfs4_unlock_state();
 }
 
 void