Received-SPF: pass (google.com: domain of linux-nfs-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <8cd63730f7b5f3e2aa3bde98587de0c6a42b384b.camel@kernel.org>
Subject: Re: nfs4.1+: workaround for defunct clientaddr?
From:   Jeff Layton <jlayton@kernel.org>
To:     Manfred Schwarb <manfred99@gmx.ch>, linux-nfs@vger.kernel.org
Date:   Mon, 03 Oct 2022 07:39:02 -0400
In-Reply-To: <39bf58c7-47d9-744b-6d26-d672aa713024@gmx.ch>
References: <39bf58c7-47d9-744b-6d26-d672aa713024@gmx.ch>
Content-Type: text/plain; charset="ISO-8859-15"
Content-Transfer-Encoding: quoted-printable
User-Agent: Evolution 3.44.4 (3.44.4-2.fc36) 
MIME-Version: 1.0
Precedence: bulk

On Sun, 2022-10-02 at 14:35 +0200, Manfred Schwarb wrote:
> Hi,
>=20
> I have 2 boxes connected with 2 network cards each, one
> crossover connection and one connection via LAN.
> I want to use the crossover connection for backup,
> so I want to be able to select exactly this wire when
> doing my NFS backup transfers. Everything interconnected via NFS4.1
> and automount.
>=20
> Now the thing is, if there is an already existing connection
> via LAN, I am not able to select the crossover connection,
> there is some session reuse against my will.
>=20
> automount config:
> /net/192.168.99.1  -fstype=3Dnfs4,nfsvers=3D4,minorversion=3D1,clientaddr=
=3D192.168.99.100   /  192.168.99.1:/
> /net2/192.168.98.1 -fstype=3Dnfs4,nfsvers=3D4,minorversion=3D1,clientaddr=
=3D192.168.98.100   /  192.168.98.1:/
>=20
> mount -l:
> 192.168.99.1:/data on /net/192.168.99.1/data type nfs4 (...,clientaddr=3D=
192.168.99.100,addr=3D192.168.99.1)
> 192.168.99.1:/data on /net2/192.168.98.1/data type nfs4 (...,clientaddr=
=3D192.168.99.100,addr=3D192.168.99.1)
>=20
> As you see, both connections are on "192.168.99.1:/data", and the backup =
runs
> over the same wire as all user communication, which is not desired.
> This even happens if I explicitly set some clientaddr=3D option.
>=20
> Now I found two workarounds:
> - downgrade to NFS 4.0, clientaddr seems to work with it
> - choose different NFS versions, i.e. one connection with
>   minorversion=3D1 and the other with minorversion=3D2
>=20
> Both possibilities seem a bit lame to me.
> Are there some other (recommended) variants which do what I want?
>=20
> It seems different minor versions result in different "nfs4_unique_id" va=
lues,
> and therefore no session sharing occurs. But why do different network
> interfaces (via explicitly set clientaddr=3D by user) not result in diffe=
rent
> "nfs4_unique_id" values?
>=20
> Thanks for any comments and advice,
> Manfred

That sounds like a bug. We probably need to compare the clientaddr
values in nfs_compare_super or nfs_compare_mount_options so that it
doesn't match if the clientaddrs are different.

As a workaround, you can probably mount the second mount with
-o nosharecache and get what you want.
--=20
Jeff Layton <jlayton@kernel.org>