On Tue, May 23, 2017, at 11:31 AM, Jeff Layton wrote:

nfsdcltrack was originally nfsdcld, a long running daemon that used
rpc_pipefs to talk to the kernel. That meant that you had to make sure
it gets enabled by systemd (or sysvinit, etc). If it dies, then you also
want to ensure that it gets restarted lest the kernel server hang,
etc...

It was pretty universally hated, as it was just one more daemon that you
needed to run to work a proper nfs server. So, I was encouraged to
switch it to a call_usermodehelper upcall and since then it has just
worked, as long as the binary is installed.

Note that with the "read()/write() fd" model you don't need
a whole process just to do that...the functionality could be rolled into systemd
or equivalent easily enough.

"You're doing it wrong. You just need to run all of these services as
long-running daemons."

Also, I imagine we could figure out a clean model to do *activation*
from kernel -> userspace too.  systemd's socket activation model
where pid 1 activates units on demand is quite nice and obviates
the need to configure things on in advance.