NFSv4: Fix a NFSv4 state manager deadlock

Fix a deadlock whereby the NFSv4 state manager can get stuck in the
delegation return code, waiting for a layout return to complete in
another thread. If the server reboots before that other thread
completes, then we need to be able to start a second state
manager thread in order to perform recovery.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

fs/nfs/nfs4_fs.h

@@ -41,6 +41,8 @@ enum nfs4_client_state {
 	NFS4CLNT_MOVED,
 	NFS4CLNT_LEASE_MOVED,
 	NFS4CLNT_DELEGATION_EXPIRED,
+	NFS4CLNT_RUN_MANAGER,
+	NFS4CLNT_DELEGRETURN_RUNNING,
 };
 
 #define NFS4_RENEW_TIMEOUT		0x01