NFSv4.1: new flag for state renewal check

Data servers not sharing a session with the mount MDS always have an empty
cl_superblocks list.
Replace the cl_superblocks empty list check to see if it is time to shut down
renewd with the NFS_CS_STOP_RENEW bit which is not set by such a data server.

Signed-off-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/nfs4renewd.c b/fs/nfs/nfs4renewd.c
index 402143d..df8e7f3 100644
--- a/fs/nfs/nfs4renewd.c
+++ b/fs/nfs/nfs4renewd.c
@@ -64,12 +64,8 @@
 	ops = clp->cl_mvops->state_renewal_ops;
 	dprintk("%s: start\n", __func__);
 
-	rcu_read_lock();
-	if (list_empty(&clp->cl_superblocks)) {
-		rcu_read_unlock();
+	if (test_bit(NFS_CS_STOP_RENEW, &clp->cl_res_state))
 		goto out;
-	}
-	rcu_read_unlock();
 
 	spin_lock(&clp->cl_lock);
 	lease = clp->cl_lease_time;