nfsd: protect clid and verifier generation with client_lock

The clid counter is a global counter currently. Move it to be a per-net
property so that it can be properly protected by the nn->client_lock
instead of relying on the client_mutex.

The verifier generator is also potentially racy if there are two
simultaneous callers. Generate the verifier when we generate the clid
value, so it's also created under the client_lock. With this, there's
no need to keep two counters as they'd always be in sync anyway, so
just use the clientid_counter for both.

As Trond points out, what would be best is to eventually move this
code to use IDR instead of the hash tables. That would also help ensure
uniqueness, but that's probably best done as a separate project.

Signed-off-by: Jeff Layton <jlayton@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/fs/nfsd/netns.h b/fs/nfsd/netns.h
index e1f479c..3831ef6 100644
--- a/fs/nfsd/netns.h
+++ b/fs/nfsd/netns.h
@@ -92,9 +92,7 @@
 	bool nfsd_net_up;
 	bool lockd_up;
 
-	/*
-	 * Time of server startup
-	 */
+	/* Time of server startup */
 	struct timeval nfssvc_boot;
 
 	/*
@@ -103,6 +101,8 @@
 	 */
 	unsigned int max_connections;
 
+	u32 clientid_counter;
+
 	struct svc_serv *nfsd_serv;
 };