Before 2.4.7, the Linux NFS client did not support NFS over TCP.
Before 2.4.20, the Linux NFS client used a heuristic to determine
whether cached file data was still valid rather than using the
standard close-to-open cache coherency method described above.
Starting with 2.4.22, the Linux NFS client employs a Van
Jacobsen-based RTT estimator to determine retransmit timeout
values when using NFS over UDP.
Before 2.6.0, the Linux NFS client did not support NFS version 4.
Before 2.6.8, the Linux NFS client used only synchronous reads
and writes when the rsize and wsize settings were smaller than
the system's page size.
The Linux client's support for protocol versions depend on
whether the kernel was built with options CONFIG_NFS_V2,
CONFIG_NFS_V3, CONFIG_NFS_V4, CONFIG_NFS_V4_1, and
CONFIG_NFS_V4_2.
