probe::nfs.proc.read.3stap man page
probe::nfs.proc.read — NFS client synchronously reads file from server
IP address of server
the file offset
used to set task->tk_flags in rpc_init_task function
read bytes in this execution
All the nfs.proc.read kernel functions were removed in kernel commit 8e0969 in December 2006, so these probes do not exist on Linux 2.6.21 and newer kernels.