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    SubjectRe: [RFC 0/13] extents and 48bit ext3
    Andrew Morton wrote:
    > On Fri, 09 Jun 2006 11:40:03 -0400
    > Jeff Garzik <jeff@garzik.org> wrote:
    >
    >> 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.
    >
    > The same happens if we create ext4 - earlier kernels don't support that,
    > either.
    >
    > I suppose we could call it ext4, although that wouldn't make much
    > difference operationally. The developers would probably choose to generate
    > ext4 from the same codebase as ext3 for maintainability reasons, rather
    > than choosing to copy-n-modify. We'd need to see the patches to be able to
    > finally make that judgement.

    I would propose the obvious... 'cp -a ext3 ext4', apply the extent and
    48bit patches, and then do the obvious search-n-replace.

    I guarantee that developer momentum would take over from there. Rather
    than fundamentally change ext3, let's let it stabilize.


    >> And as features continue to be added in this manner, this problem gets
    >> _exponentially_ worse.
    >
    > "continue to be added"? afaik this is the first time this has happened,
    > and there's no plan to do it again.

    ext3 developers are _fundamentally changing_ the block allocation
    structure [in a good way]. If they can get away with it once, they will
    continue to modify ext3, adding btrees and other new gadgets. That's
    just human nature. For example, htree was a minor disaster,
    deployment-wise, on the distro vendor side.

    I think extents and 48bit are so fundamental that it's silly to attempt
    to minimize the impact from the user's perspective, and moreover, I
    think Linux benefits more if ext3 is _not_ kept on life support this way.

    We need to draw a line in the sand. If we don't, no one ever will.

    Jeff



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