Provided by: systemtap-doc_2.3-1ubuntu1.4_all 

NAME
probe::nfsd.read - NFS server reading data from a file for client
SYNOPSIS
nfsd.read
VALUES
size
read bytes
file
argument file, indicates if the file has been opened.
client_ip
the ip address of client
vlen
read blocks
offset
the offset of file
fh
file handle (the first part is the length of the file handle)
vec
struct kvec, includes buf address in kernel address and length of each buffer
count
read bytes
SystemTap Tapset Reference March 2016 PROBE::NFSD.READ(3stap)