NFSv41: Resend on NFS4ERR_RETRY_UNCACHED_REP

Free the slot and resend the RPC with new session <slot#,seq#>.

For nfs4_async_handle_error, return -EAGAIN and set the task->tk_status to 0
to restart the async rpc in the rpc_restart_call_prepare state which resets
the slot.

For nfs4_handle_exception, retrying a call that uses nfs4_call_sync will
reset the slot via nfs41_call_sync_prepare.

For open/close/lock/locku/delegreturn/layoutcommit/unlink/rename/write
cachethis is true, so these operations will not trigger an
NFS4ERR_RETRY_UNCACHED_REP.

Signed-off-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/nfs4filelayout.c

@@ -117,6 +117,8 @@ static int filelayout_async_handle_error(struct rpc_task *task,
 	case -EKEYEXPIRED:
 		rpc_delay(task, FILELAYOUT_POLL_RETRY_MAX);
 		break;
+	case -NFS4ERR_RETRY_UNCACHED_REP:
+		break;
 	default:
 		dprintk("%s DS error. Retry through MDS %d\n", __func__,
 			task->tk_status);

fs/nfs/nfs4proc.c

@@ -300,6 +300,7 @@ static int nfs4_handle_exception(struct nfs_server *server, int errorcode, struc
 			ret = nfs4_delay(server->client, &exception->timeout);
 			if (ret != 0)
 				break;
+		case -NFS4ERR_RETRY_UNCACHED_REP:
 		case -NFS4ERR_OLD_STATEID:
 			exception->retry = 1;
 			break;
@@ -3695,6 +3696,7 @@ nfs4_async_handle_error(struct rpc_task *task, const struct nfs_server *server,
 			rpc_delay(task, NFS4_POLL_RETRY_MAX);
 			task->tk_status = 0;
 			return -EAGAIN;
+		case -NFS4ERR_RETRY_UNCACHED_REP:
 		case -NFS4ERR_OLD_STATEID:
 			task->tk_status = 0;
 			return -EAGAIN;
@@ -4844,6 +4846,8 @@ static void nfs4_get_lease_time_done(struct rpc_task *task, void *calldata)
 		dprintk("%s Retry: tk_status %d\n", __func__, task->tk_status);
 		rpc_delay(task, NFS4_POLL_RETRY_MIN);
 		task->tk_status = 0;
+		/* fall through */
+	case -NFS4ERR_RETRY_UNCACHED_REP:
 		nfs_restart_rpc(task, data->clp);
 		return;
 	}
@@ -5479,6 +5483,8 @@ static int nfs41_reclaim_complete_handle_errors(struct rpc_task *task, struct nf
 		break;
 	case -NFS4ERR_DELAY:
 		rpc_delay(task, NFS4_POLL_RETRY_MAX);
+		/* fall through */
+	case -NFS4ERR_RETRY_UNCACHED_REP:
 		return -EAGAIN;
 	default:
 		nfs4_schedule_lease_recovery(clp);