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);