nfs41: Use BIND_CONN_TO_SESSION for CB_PATH_DOWN*

The state manager can handle SEQ4_STATUS_CB_PATH_DOWN* flags with a
BIND_CONN_TO_SESSION instead of destroying the session and creating a new one.
Signed-off-by: Weston Andros Adamson <dros@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/nfs4_fs.h

@@ -25,6 +25,7 @@ enum nfs4_client_state {
 	NFS4CLNT_LEASE_CONFIRM,
 	NFS4CLNT_SERVER_SCOPE_MISMATCH,
 	NFS4CLNT_PURGE_STATE,
+	NFS4CLNT_BIND_CONN_TO_SESSION,
 };
 
 enum nfs4_session_state {

fs/nfs/nfs4state.c

@@ -1640,13 +1640,20 @@ static void nfs41_handle_recallable_state_revoked(struct nfs_client *clp)
 	nfs_expire_all_delegations(clp);
 }
 
-static void nfs41_handle_cb_path_down(struct nfs_client *clp)
+static void nfs41_handle_backchannel_fault(struct nfs_client *clp)
 {
 	nfs_expire_all_delegations(clp);
 	if (test_and_set_bit(NFS4CLNT_SESSION_RESET, &clp->cl_state) == 0)
 		nfs4_schedule_state_manager(clp);
 }
 
+static void nfs41_handle_cb_path_down(struct nfs_client *clp)
+{
+	if (test_and_set_bit(NFS4CLNT_BIND_CONN_TO_SESSION,
+		&clp->cl_state) == 0)
+		nfs4_schedule_state_manager(clp);
+}
+
 void nfs41_handle_sequence_flag_errors(struct nfs_client *clp, u32 flags)
 {
 	if (!flags)
@@ -1664,8 +1671,9 @@ void nfs41_handle_sequence_flag_errors(struct nfs_client *clp, u32 flags)
 		nfs41_handle_state_revoked(clp);
 	if (flags & SEQ4_STATUS_RECALLABLE_STATE_REVOKED)
 		nfs41_handle_recallable_state_revoked(clp);
-	if (flags & (SEQ4_STATUS_CB_PATH_DOWN |
-			    SEQ4_STATUS_BACKCHANNEL_FAULT |
+	if (flags & SEQ4_STATUS_BACKCHANNEL_FAULT)
+		nfs41_handle_backchannel_fault(clp);
+	else if (flags & (SEQ4_STATUS_CB_PATH_DOWN |
 				SEQ4_STATUS_CB_PATH_DOWN_SESSION))
 		nfs41_handle_cb_path_down(clp);
 }
@@ -1691,6 +1699,7 @@ static int nfs4_reset_session(struct nfs_client *clp)
 	clear_bit(NFS4CLNT_SESSION_RESET, &clp->cl_state);
 	/* create_session negotiated new slot table */
 	clear_bit(NFS4CLNT_RECALL_SLOT, &clp->cl_state);
+	clear_bit(NFS4CLNT_BIND_CONN_TO_SESSION, &clp->cl_state);
 
 	 /* Let the state manager reestablish state */
 	if (!test_bit(NFS4CLNT_LEASE_EXPIRED, &clp->cl_state))
@@ -1727,10 +1736,19 @@ static int nfs4_recall_slot(struct nfs_client *clp)
 	return 0;
 }
 
+static int nfs4_bind_conn_to_session(struct nfs_client *clp)
+{
+	return nfs4_proc_bind_conn_to_session(clp);
+}
 #else /* CONFIG_NFS_V4_1 */
 static int nfs4_reset_session(struct nfs_client *clp) { return 0; }
 static int nfs4_end_drain_session(struct nfs_client *clp) { return 0; }
 static int nfs4_recall_slot(struct nfs_client *clp) { return 0; }
+
+static int nfs4_bind_conn_to_session(struct nfs_client *clp)
+{
+	return 0;
+}
 #endif /* CONFIG_NFS_V4_1 */
 
 /* Set NFS4CLNT_LEASE_EXPIRED for all v4.0 errors and for recoverable errors
@@ -1814,6 +1832,14 @@ static void nfs4_state_manager(struct nfs_client *clp)
 				goto out_error;
 		}
 
+		/* Send BIND_CONN_TO_SESSION */
+		if (test_and_clear_bit(NFS4CLNT_BIND_CONN_TO_SESSION,
+				&clp->cl_state) && nfs4_has_session(clp)) {
+			status = nfs4_bind_conn_to_session(clp);
+			if (status < 0)
+				goto out_error;
+		}
+
 		/* First recover reboot state... */
 		if (test_bit(NFS4CLNT_RECLAIM_REBOOT, &clp->cl_state)) {
 			status = nfs4_do_reclaim(clp,