Add pread/pwrite support to sync engine

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/fio.1 b/fio.1
index aacee10..35056a8 100644
--- a/fio.1
+++ b/fio.1
@@ -209,6 +209,9 @@
 Basic \fIread\fR\|(2) or \fIwrite\fR\|(2) I/O.  \fIfseek\fR\|(2) is used to
 position the I/O location.
 .TP
+.B psync
+Basic \fIpread\fR\|(2) or \fIpwrite\fR\|(2) I/O.
+.TP
 .B libaio
 Linux native asynchronous I/O.
 .TP