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From: "Lever, Charles" <Charles.Lever@netapp.com>
To: "'Neil Brown'" <neilb@cse.unsw.edu.au>
Cc: Jeff Garzik <jgarzik@mandrakesoft.com>, linux-kernel@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, phil@off.net,
        "Peter J. Braam" <braam@clusterfs.com>
Subject: RE: tmpfs, NFS, file handles
Date: Thu, 21 Feb 2002 08:16:04 -0800
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> That means you are only hashing inodes exported by NFS, and you have
> a pretty good guarantee of uniqueness (providing time doesn't go
> backwards).

this may be obvious... apologies.

don't use the TOD directly -- it can go backwards if ntpd or an admin
sets it back.  better to use a monotonically increasing number that
you completely control yourself.

also, if your timer resolution isn't good enough, a window opens 
where two generated "uniquifiers" can be the same for all intents
and purposes.

if there's nothing else we've learned from NFS, it's that using
timestamps is a lousy way of managing cache coherency and file
identity.  ;-)
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