From the Linux Client Guide:
"Mounting functions are almost identical on the Linux and Solaris clients. However, the mount options available for the Linux client are limited to the following:
- rw, ro
- retry
- shared
- meta_timeo
- rdlease, wrlease, aplease
- minallocsz, maxallocsz
- min_pool (ignored outside of samfs.cmd)
- noauto, auto (ignored outside of /etc/fstab)
No other mount options are available for the Linux client."
So you do not have the reader option in Linux.