nfsd4: fix v4 state shutdown error paths

If someone tries to shut down the laundry_wq while it isn't up it'll
cause an oops.

This can happen because write_ports can create a nfsd_svc before we
really start the nfs server, and we may fail before the server is ever
started.

Also make sure state is shutdown on error paths in nfsd_svc().

Use a common global nfsd_up flag instead of nfs4_init, and create common
helper functions for nfsd start/shutdown, as there will be other work
that we want done only when we the number of nfsd threads transitions
between zero and nonzero.
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

fs/nfsd/nfs4state.c

@@ -51,7 +51,6 @@ static time_t boot_time;
 static u32 current_ownerid = 1;
 static u32 current_fileid = 1;
 static u32 current_delegid = 1;
-static u32 nfs4_init;
 static stateid_t zerostateid;             /* bits all 0 */
 static stateid_t onestateid;              /* bits all 1 */
 static u64 current_sessionid = 1;
@@ -4071,16 +4070,8 @@ __nfs4_state_start(void)
 int
 nfs4_state_start(void)
 {
-	int ret;
-
-	if (nfs4_init)
-		return 0;
 	nfsd4_load_reboot_recovery_data();
-	ret = __nfs4_state_start();
-	if (ret)
-		return ret;
-	nfs4_init = 1;
-	return 0;
+	return __nfs4_state_start();
 }
 
 static void
@@ -4115,7 +4106,6 @@ __nfs4_state_shutdown(void)
 	}
 
 	nfsd4_shutdown_recdir();
-	nfs4_init = 0;
 }
 
 void

fs/nfsd/nfssvc.c

@@ -180,6 +180,31 @@ int nfsd_nrthreads(void)
 	return rv;
 }
 
+static bool nfsd_up = false;
+
+static int nfsd_startup(unsigned short port, int nrservs)
+{
+	int ret;
+
+	ret = nfs4_state_start();
+	nfsd_up = true;
+	return ret;
+}
+
+static void nfsd_shutdown(void)
+{
+	/*
+	 * write_ports can create the server without actually starting
+	 * any threads--if we get shut down before any threads are
+	 * started, then nfsd_last_thread will be run before any of this
+	 * other initialization has been done.
+	 */
+	if (!nfsd_up)
+		return;
+	nfs4_state_shutdown();
+	nfsd_up = false;
+}
+
 static void nfsd_last_thread(struct svc_serv *serv)
 {
 	/* When last nfsd thread exits we need to do some clean-up */
@@ -188,7 +213,7 @@ static void nfsd_last_thread(struct svc_serv *serv)
 		lockd_down();
 	nfsd_serv = NULL;
 	nfsd_racache_shutdown();
-	nfs4_state_shutdown();
+	nfsd_shutdown();
 
 	printk(KERN_WARNING "nfsd: last server has exited, flushing export "
 			    "cache\n");
@@ -380,6 +405,7 @@ int
 nfsd_svc(unsigned short port, int nrservs)
 {
 	int	error;
+	bool	first_thread;
 
 	mutex_lock(&nfsd_mutex);
 	dprintk("nfsd: creating service\n");
@@ -395,19 +421,23 @@ nfsd_svc(unsigned short port, int nrservs)
 	error =	nfsd_racache_init(2*nrservs);
 	if (error<0)
 		goto out;
-	error = nfs4_state_start();
-	if (error)
-		goto out;
+
+	first_thread = (nfsd_serv->sv_nrthreads == 0) && (nrservs != 0);
+
+	if (first_thread) {
+		error = nfsd_startup(port, nrservs);
+		if (error)
+			goto out;
+	}
 
 	nfsd_reset_versions();
 
 	error = nfsd_create_serv();
-
 	if (error)
-		goto out;
+		goto out_shutdown;
 	error = nfsd_init_socks(port);
 	if (error)
-		goto failure;
+		goto out_destroy;
 
 	error = svc_set_num_threads(nfsd_serv, NULL, nrservs);
 	if (error == 0)
@@ -416,9 +446,12 @@ nfsd_svc(unsigned short port, int nrservs)
 		 * so subtract 1
 		 */
 		error = nfsd_serv->sv_nrthreads - 1;
- failure:
+out_destroy:
 	svc_destroy(nfsd_serv);		/* Release server */
- out:
+out_shutdown:
+	if (error < 0 && first_thread)
+		nfsd_shutdown();
+out:
 	mutex_unlock(&nfsd_mutex);
 	return error;
 }