NFSD: replace delayed_work with work_struct for nfsd_client_shrinker

Since nfsd4_state_shrinker_count always calls mod_delayed_work with
0 delay, we can replace delayed_work with work_struct to save some
space and overhead.

Also add the call to cancel_work after unregister the shrinker
in nfs4_state_shutdown_net.
Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/netns.h

@@ -195,7 +195,7 @@ struct nfsd_net {
 
 	atomic_t		nfsd_courtesy_clients;
 	struct shrinker		nfsd_client_shrinker;
-	struct delayed_work	nfsd_shrinker_work;
+	struct work_struct	nfsd_shrinker_work;
 };
 
 /* Simple check to find out if a given net was properly initialized */

fs/nfsd/nfs4state.c

@@ -4411,7 +4411,7 @@ nfsd4_state_shrinker_count(struct shrinker *shrink, struct shrink_control *sc)
 	if (!count)
 		count = atomic_long_read(&num_delegations);
 	if (count)
-		mod_delayed_work(laundry_wq, &nn->nfsd_shrinker_work, 0);
+		queue_work(laundry_wq, &nn->nfsd_shrinker_work);
 	return (unsigned long)count;
 }
 
@@ -6225,8 +6225,7 @@ deleg_reaper(struct nfsd_net *nn)
 static void
 nfsd4_state_shrinker_worker(struct work_struct *work)
 {
-	struct delayed_work *dwork = to_delayed_work(work);
-	struct nfsd_net *nn = container_of(dwork, struct nfsd_net,
+	struct nfsd_net *nn = container_of(work, struct nfsd_net,
 				nfsd_shrinker_work);
 
 	courtesy_client_reaper(nn);
@@ -8056,7 +8055,7 @@ static int nfs4_state_create_net(struct net *net)
 	INIT_LIST_HEAD(&nn->blocked_locks_lru);
 
 	INIT_DELAYED_WORK(&nn->laundromat_work, laundromat_main);
-	INIT_DELAYED_WORK(&nn->nfsd_shrinker_work, nfsd4_state_shrinker_worker);
+	INIT_WORK(&nn->nfsd_shrinker_work, nfsd4_state_shrinker_worker);
 	get_net(net);
 
 	nn->nfsd_client_shrinker.scan_objects = nfsd4_state_shrinker_scan;
@@ -8163,6 +8162,7 @@ nfs4_state_shutdown_net(struct net *net)
 	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
 
 	unregister_shrinker(&nn->nfsd_client_shrinker);
+	cancel_work(&nn->nfsd_shrinker_work);
 	cancel_delayed_work_sync(&nn->laundromat_work);
 	locks_end_grace(&nn->nfsd4_manager);