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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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