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

Sven-Haegar Koch
2006-06-10T00:49:34Z

On Fri, 9 Jun 2006, Michael Poole wrote:

> Jeff Garzik writes:
>
>> Andrew Morton wrote:
>>> Ted&co have been pretty good at avoiding compatibility problems.
>>
>> Well, extents and 48bit make that track record demonstrably worse.
>>
>> Users are now forced to remember that, if they write to their
>> filesystem after using either $mmver or $korgver kernels, they are
>> locked out of using older kernels.
>
> Users are also forced to remember that, if they use certain new
> distros or programs, they are locked out of using older kernels. They
> are forced to remember that if they have certain newer hardware, they
> are locked out of using older kernels. They are forced to remember
> that if they use ext3 (or XFS or JFS) _at all_ they are locked out of
> using older kernels. Why single out this particular aspect of limited
> forward compatibility to harp on so much?

I see a different problem with "ext3 + extends is not ext3 anymore" when
the feature goes mainstream:
- user with old distri, no extends in use, no kernel support for them
- user has some kind of problem
- uses new rescue disk (aka knoppix at the time of problem) - that then
is current stuff, and certainly uses extents - fixes problem on disk
(may be a simple as running lilo/grub from chroot, happens often for me)
- tries to boot back into his distri -> *boom* he lost

c'ya
sven

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