NFS: Migration support for RELEASE_LOCKOWNER

Currently the Linux NFS client ignores the operation status code for
the RELEASE_LOCKOWNER operation.  Like NFSv3's UMNT operation,
RELEASE_LOCKOWNER is a courtesy to help servers manage their
resources, and the outcome is not consequential for the client.

During a migration, a server may report NFS4ERR_LEASE_MOVED, in
which case the client really should retry, since typically
LEASE_MOVED has nothing to do with the current operation, but does
prevent it from going forward.

Also, it's important for a client to respond as soon as possible to
a moved lease condition, since the client's lease could expire on
the destination without further action by the client.

NFS4ERR_DELAY is not included in the list of valid status codes for
RELEASE_LOCKOWNER in RFC 3530bis.  However, rfc3530-migration-update
does permit migration-capable servers to return DELAY to clients,
but only in the context of an ongoing migration.  In this case the
server has frozen lock state in preparation for migration, and a
client retry would help the destination server purge unneeded state
once migration recovery is complete.

Interestly, NFS4ERR_MOVED is not valid for RELEASE_LOCKOWNER, even
though lock owners can be migrated with Transparent State Migration.

Note that RFC 3530bis section 9.5 includes RELEASE_LOCKOWNER in the
list of operations that renew a client's lease on the server if they
succeed.  Now that our client pays attention to the operation's
status code, we can note that renewal appropriately.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/nfs4proc.c

@@ -5800,6 +5800,7 @@ struct nfs_release_lockowner_data {
 	struct nfs_release_lockowner_args args;
 	struct nfs4_sequence_args seq_args;
 	struct nfs4_sequence_res seq_res;
+	unsigned long timestamp;
 };
 
 static void nfs4_release_lockowner_prepare(struct rpc_task *task, void *calldata)
@@ -5807,12 +5808,27 @@ static void nfs4_release_lockowner_prepare(struct rpc_task *task, void *calldata
 	struct nfs_release_lockowner_data *data = calldata;
 	nfs40_setup_sequence(data->server,
 				&data->seq_args, &data->seq_res, task);
+	data->timestamp = jiffies;
 }
 
 static void nfs4_release_lockowner_done(struct rpc_task *task, void *calldata)
 {
 	struct nfs_release_lockowner_data *data = calldata;
+	struct nfs_server *server = data->server;
+
 	nfs40_sequence_done(task, &data->seq_res);
+
+	switch (task->tk_status) {
+	case 0:
+		renew_lease(server, data->timestamp);
+		break;
+	case -NFS4ERR_STALE_CLIENTID:
+	case -NFS4ERR_EXPIRED:
+	case -NFS4ERR_LEASE_MOVED:
+	case -NFS4ERR_DELAY:
+		if (nfs4_async_handle_error(task, server, NULL) == -EAGAIN)
+			rpc_restart_call_prepare(task);
+	}
 }
 
 static void nfs4_release_lockowner_release(void *calldata)