From owner-freebsd-current@FreeBSD.ORG  Tue Jul 20 17:28:30 2004
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
Delivered-To: freebsd-current@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id 37EFC16A4CE
	for <current@freebsd.org>; Tue, 20 Jul 2004 17:28:30 +0000 (GMT)
Received: from pimout2-ext.prodigy.net (pimout2-ext.prodigy.net
	[207.115.63.101])
	by mx1.FreeBSD.org (Postfix) with ESMTP id 9EEA843D66
	for <current@freebsd.org>; Tue, 20 Jul 2004 17:28:29 +0000 (GMT)
	(envelope-from julian@elischer.org)
Received: from elischer.org (adsl-68-121-219-69.dsl.snfc21.pacbell.net
	[68.121.219.69])i6KHSLUK239090;	Tue, 20 Jul 2004 13:28:23 -0400
Message-ID: <40FD5634.5040000@elischer.org>
Date: Tue, 20 Jul 2004 10:28:20 -0700
From: Julian Elischer <julian@elischer.org>
User-Agent: Mozilla/5.0 (X11; U; FreeBSD i386; en-US; rv:1.4b) Gecko/20030524
X-Accept-Language: en, hu
MIME-Version: 1.0
To: Peter Jeremy <PeterJeremy@optushome.com.au>
References: <40F963D8.6010201@freebsd.org>
	<20040719060730.GA87697@nagual.pp.ru> <40FC9FC2.8050400@kientzle.com>
	<20040720081051.GB3001@cirb503493.alcatel.com.au>
In-Reply-To: <20040720081051.GB3001@cirb503493.alcatel.com.au>
Content-Type: text/plain; charset=us-ascii; format=flowed
Content-Transfer-Encoding: 7bit
cc: current@freebsd.org
cc: Andrey Chernov <ache@nagual.pp.ru>
Subject: Re: NEW TAR
X-BeenThere: freebsd-current@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: Discussions about the use of FreeBSD-current
	<freebsd-current.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-current>
List-Post: <mailto:freebsd-current@freebsd.org>
List-Help: <mailto:freebsd-current-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Tue, 20 Jul 2004 17:28:30 -0000

Peter Jeremy wrote:

>On Mon, 2004-Jul-19 21:29:54 -0700, Tim Kientzle wrote:
>  
>
>>I have some ideas about sparse file handling,
>>but they're not gtar-compatible.  (The gtar
>>approach has a number of drawbacks.  The primary
>>one being that on many systems it requires reading
>>the entire file twice, once to find holes and again
>>to actually archive the file.
>>    
>>
>
>Actually, it's not possible to accurately determine the holes in a
>file by reading it - you can't differentiate between a hole and a
>allocated block of zeroes.  What you need is a (new) syscall that
>invokes a new VOP_... and returns a bitmap of allocated blocks.  This
>would be non-trival unfortunately.
>

OR, given the right flags, note all blocks of zeros as if they were 
unallocated,
and write them that way.. regardless of how it was in the original file.

>
>  
>