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Date:      Fri, 02 Mar 2001 01:32:33 +0900
From:      "Daniel C. Sobral" <dcs@newsguy.com>
To:        Garrett Wollman <wollman@khavrinen.lcs.mit.edu>
Cc:        rwatson@FreeBSD.ORG, arch@FreeBSD.ORG
Subject:   Re: Arch question for a UDF FS driver
Message-ID:  <3A9E79A1.C56F93DF@newsguy.com>
References:  <mit.lcs.mail.freebsd-arch/200103010510.WAA16907@usr05.primenet.com> <200103011420.JAA00305@khavrinen.lcs.mit.edu>

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Garrett Wollman wrote:
> 
> >There are, unfortunately, a few apps that make use of the inode
> >number returned by stat -- generally to try and detect hard links (I
> >think tar does this).
> 
> As I have pointed out before, it is a requirement of POSIX that
> distinct files have distinct (device, inode) pairs.  The individual
> st_dev and st_ino values are not required to have any particular
> meaning except when used together in this way.  (So, it's possible to
> treat the pair of members as a single 64-bit quantity, should that be
> desired, provided that uniqueness can be guaranteed.)

And as have been answered before, that POSIX requirement is not viable
with some modern distributed filesystems. Some have identifiers greater
than 64 bits. And some do not have identifiers that uniquely identify a
file at all (you'd have to compare each new identifier acquired with all
cached identifiers to check for uniqueness).

-- 
Daniel C. Sobral			(8-DCS)
dcs@newsguy.com
dcs@freebsd.org
capo@the.obscure.bsdconspiracy.net

	I think you are delusional, but that is OK. Its part of your natural
charm!

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