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Date: Fri, 09 Jun 2006 16:31:17 -0400
From: Jeff Garzik <jeff@garzik.org>
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To: Linus Torvalds <torvalds@osdl.org>, Alex Tomas <alex@clusterfs.com>,
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       ext2-devel <ext2-devel@lists.sourceforge.net>,
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Subject: Re: [Ext2-devel] [RFC 0/13] extents and 48bit ext3
References: <44898EE3.6080903@garzik.org> <448992EB.5070405@garzik.org> <Pine.LNX.4.64.0606090836160.5498@g5.osdl.org> <m33beecntr.fsf@bzzz.home.net> <Pine.LNX.4.64.0606090913390.5498@g5.osdl.org> <Pine.LNX.4.64.0606090933130.5498@g5.osdl.org> <20060609181020.GB5964@schatzie.adilger.int> <Pine.LNX.4.64.0606091114270.5498@g5.osdl.org> <m31wty9o77.fsf@bzzz.home.net> <Pine.LNX.4.64.0606091137340.5498@g5.osdl.org> <20060609201643.GG5964@schatzie.adilger.int>
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Andreas Dilger wrote:
> The other issue is that adding a new "ext4" filesystem type will cause
> userspace tools to break that assume they know something about the
> filesystem type.  They will all detect the filesystem as "ext3" and try
> to mount it as such, when the required kernel filesystem is ext4.  Or
> we will need to have "mkfs.ext4", "fsck.ext4", etc, for no particular
> reason.

Yes, you want those tools, and you want to call the filesystem ext4. 
Otherwise you'll never break free of the existing metadata formats 
(which are apparently changing over time _anyway_).


> Either a system upgrades totally to ext4 to avoid the duplication of code
> in memory (and breaks ALL backward compatibility, for no good reason), or

Correct.  You must upgrade totally to ext4.

And this happens ANYWAY once extents/etc. are enabled.  Its an upgrade.

	Jeff