lockd: get rid of reference-counted NSM RPC clients

Currently we have reference-counted per-net NSM RPC client
which created on the first monitor request and destroyed
after the last unmonitor request. It's needed because
RPC client need to know 'utsname()->nodename', but utsname()
might be NULL when nsm_unmonitor() called.

So instead of holding the rpc client we could just save nodename
in struct nlm_host and pass it to the rpc_create().
Thus ther is no need in keeping rpc client until last
unmonitor request. We could create separate RPC clients
for each monitor/unmonitor requests.

Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/lockd/svc.c

@@ -592,7 +592,6 @@ static int lockd_init_net(struct net *net)
 	INIT_DELAYED_WORK(&ln->grace_period_end, grace_ender);
 	INIT_LIST_HEAD(&ln->lockd_manager.list);
 	ln->lockd_manager.block_opens = false;
-	spin_lock_init(&ln->nsm_clnt_lock);
 	INIT_LIST_HEAD(&ln->nsm_handles);
 	return 0;
 }