On Mon, Mar 01 2021, J. Bruce Fields wrote:

> I've gotten requests for similar functionality, and intended to
> implement it using directory notifications on /proc/fs/nfsd/clients.

I've been exploring this a bit.
When I mount a filesystem, 2 clients get created.
With NFSv4.0, the second client is immediately deleted, and the first
client is deleted one grace period after the filesystem is unmounted.
With NFSv4.1 and 4.2, the first client is immediately deleted, and the
second client is deleted immediately after the unmount.

Do you know why two clients are created?  I could dig through the code
... but maybe you already know.

Thanks,
NeilBrown