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    SubjectRe: [RFC] file extents for EXT3
    On Aug 11, 2003  08:53 -0400, Jeff Garzik wrote:
    > Changing the underlying disk format without bumping the filesystem
    > revision is a hugely bad idea. I disagreed with merging htree (even
    > though its backward compat) without bumping the filesystem version, too.
    >
    > Vendors, distributors, OEMs, etc. all test against existing on-disk
    > formats, when they release their products. When the filesystem format
    > for an existing filesystem, in production, changes underneath them, they
    > tend to get worried and annoyed. So, to all ext developers,
    >
    > Please add <it> to ext4 not ext3!

    Ext2/3 uses feature flags instead of version numbers to indicate such
    changes. Version numbers are a poor way of indicating whether a change
    is compatible or not compared to feature flags. For example, if you bump
    the minor number to indicate a "compatible" change it means that any
    code that pretends to support version x.y features also needs to support
    all features <= y and all features <= x.

    If you really want to have a feature number to be happy, just think of

    s.feature_incompat.s_feature_ro_compat.s_feature_compat

    as something like a version number and you will nearly be happy.

    Cheers, Andreas
    --
    Andreas Dilger
    http://sourceforge.net/projects/ext2resize/
    http://www-mddsp.enel.ucalgary.ca/People/adilger/

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