On Tue, Mar 02, 2021 at 02:01:36PM +1100, NeilBrown wrote: > 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. Yeah, internally it's creating an "unconfirmed client" on SETCLIENTID (or EXCHANGE_ID) and then a new "confirmed client" on SETCLIENTID_CONFIRM (or CREATE_SESSION). I'm not sure why the ordering's a little different between the 4.0/4.1+ cases. The difference on unmount is because 4.1+ clients immediately send a DESTROY_CLIENTID on unmount, but that op was new to 4.1. (Note of course this isn't precisely mount/unmount, as the same client can be used for multiple filesystems.) Honestly, I think this is exposing an implementation detail and it's dumb. I'll look into fixing it. (I don't know if that change itself would cause additional difficulty.) --b.
