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Date:   Mon, 31 Jan 2022 18:15:41 +0100 (CET)
From:   Richard Weinberger <richard@nod.at>
To:     bfields <bfields@fieldses.org>
Cc:     linux-nfs <linux-nfs@vger.kernel.org>,
        luis turcitu <luis.turcitu@appsbroker.com>,
        chris chilvers <chris.chilvers@appsbroker.com>,
        david young <david.young@appsbroker.com>,
        Daire Byrne <daire@dneg.com>,
        david oberhollenzer <david.oberhollenzer@sigma-star.at>,
        david <david@sigma-star.at>, goliath@sigma-star.at,
        trond myklebust <trond.myklebust@hammerspace.com>,
        anna schumaker <anna.schumaker@netapp.com>
Message-ID: <8290532.5517.1643649341941.JavaMail.zimbra@nod.at>
In-Reply-To: <20220131170125.GB30119@fieldses.org>
References: <20220131104316.10357-1-richard@nod.at> <20220131170125.GB30119@fieldses.org>
Subject: Re: [RFC PATCH] mountd: export: Deal with NFS filesystems
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----- Ursprüngliche Mail -----
> Von: "bfields" <bfields@fieldses.org>
>> Using /proc/fs/nfsfs/volumes it is possible to find the NFS fsid
>> from the backend and use it as seed for mountd's UUID mechanism.
> 
> Sorry, I haven't checked--what is that number, really?  It's probably
> not the fsid returned from the server, as that wouldn't be guaranteed
> unique across multiple servers.  But that means it's probably generated
> in a way that doesn't guarantee it's stable across reboots.  And we need
> filehandles to work across reboots.

Unless I badly misunderstood the code it comes from fs/nfs/client.c's
nfs_create_server() where the NFS client fetches NFS_ATTR_FATTR via getattr().
So it should be unique:
https://datatracker.ietf.org/doc/html/rfc7530#section-5.8.1.9

Thanks,
//richard