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Date:   Mon, 1 Mar 2021 22:27:33 -0500
From:   "J. Bruce Fields" <bfields@fieldses.org>
To:     NeilBrown <neilb@suse.de>
Cc:     Steve Dickson <SteveD@RedHat.com>,
        Linux NFS Mailing list <linux-nfs@vger.kernel.org>
Subject: Re: [PATCH 0/5 v2] nfs-utils: provide audit-logging of NFSv4 access
Message-ID: <20210302032733.GC16303@fieldses.org>
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 <20210301185037.GB14881@fieldses.org>
 <874khui7hr.fsf@notabene.neil.brown.name>
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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.