NFSD: simplify error paths in nfsd_svc()

The error paths in nfsd_svc() are needlessly complex and can result in a
final call to svc_put() without nfsd_last_thread() being called.  This
results in the listening sockets not being closed properly.

The per-netns setup provided by nfsd_startup_new() and removed by
nfsd_shutdown_net() is needed precisely when there are running threads.
So we don't need nfsd_up_before.  We don't need to know if it *was* up.
We only need to know if any threads are left.  If none are, then we must
call nfsd_shutdown_net().  But we don't need to do that explicitly as
nfsd_last_thread() does that for us.

So simply call nfsd_last_thread() before the last svc_put() if there are
no running threads.  That will always do the right thing.

Also discard:
 pr_info("nfsd: last server has exited, flushing export cache\n");
It may not be true if an attempt to start the first server failed, and
it isn't particularly helpful and it simply reports normal behaviour.
Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/nfssvc.c

@@ -572,7 +572,6 @@ static void nfsd_last_thread(struct net *net)
 		return;
 
 	nfsd_shutdown_net(net);
-	pr_info("nfsd: last server has exited, flushing export cache\n");
 	nfsd_export_flush(net);
 }
 
@@ -786,7 +785,6 @@ int
 nfsd_svc(int nrservs, struct net *net, const struct cred *cred)
 {
 	int	error;
-	bool	nfsd_up_before;
 	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
 	struct svc_serv *serv;
 
@@ -806,8 +804,6 @@ nfsd_svc(int nrservs, struct net *net, const struct cred *cred)
 	error = nfsd_create_serv(net);
 	if (error)
 		goto out;
-
-	nfsd_up_before = nn->nfsd_net_up;
 	serv = nn->nfsd_serv;
 
 	error = nfsd_startup_net(net, cred);
@@ -815,17 +811,15 @@ nfsd_svc(int nrservs, struct net *net, const struct cred *cred)
 		goto out_put;
 	error = svc_set_num_threads(serv, NULL, nrservs);
 	if (error)
-		goto out_shutdown;
+		goto out_put;
 	error = serv->sv_nrthreads;
-	if (error == 0)
-		nfsd_last_thread(net);
-out_shutdown:
-	if (error < 0 && !nfsd_up_before)
-		nfsd_shutdown_net(net);
 out_put:
 	/* Threads now hold service active */
 	if (xchg(&nn->keep_active, 0))
 		svc_put(serv);
+
+	if (serv->sv_nrthreads == 0)
+		nfsd_last_thread(net);
 	svc_put(serv);
 out:
 	mutex_unlock(&nfsd_mutex);