Re: [RFC 0/13] extents and 48bit ext3

[Jeff Garzik]

Overall, I'm surprised that ext3 developers don't see any of the 
problems related to progressive, stealth filesystem upgrades.

Users are never given a clear indication of when their metadata is being 
upgraded, there is no clear "line of demarcation" they cross, when they 
start using extents.

Since there is no user-visible fs upgrade event, users do not have a 
clear picture of what features are being used -- which means they are 
kept in the dark about which kernels are OK to use on their data.

Do you guys honestly expect users to keep track of which kernels added 
specific ext3 features?

This is why other enterprise filesystems have clear "fs version 1", "fs 
version 2" points across which a user migrates.  ext3's feature-flags 
approach just means that there are a million combinations of potential 
old-and-new features, in-tree and third party, all of which must be 
supported.

	Jeff


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