Messages in this thread |  | | Date | Sun, 23 Sep 2001 22:19:16 -0700 | From | Andrew Morton <> | Subject | Re: Linux-2.4.10 + ext3 |
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Aaron Lehmann wrote: > > ... > I simply was hoping for insted of: > > <*> EXT2 fs > <*> EXT3 fs > > (which is required today for most ext3-using people who want to do ext2 > mounts) > > ... there could be: > > <*> EXT2 fs > <*> EXT3 journalling extensions > > AFAIK this would eliminate a lot of duplicate kernel code for ext3 > users. >
mm.. The filesystems could be pretty much identical on the reading path, but they're quite dissimilar on the writing path. So the reading-stuff code could be commoned up.
I don't think it'd buy much, though. They are different filesystems and the fact that ext3 borrows a lot of ext2 code is a useful consequence of it having the same on-disk format.
And the main reason for having the same on-disk format is not, IMO, to ease migration between the two filesystems. That's just a once-off activity. The main reason for preserving compatibility is so that ext3 can leverage e2fsprogs, and the wealth of knowledge and understanding of ext2 performance and behaviour.
The ext2-compatibility seems to be a bit of a political albatross for ext3, really - people appear to be of the opinion that the ext3 design was somehow compromised by the compatibility requirement. This isn't so - ext3 is a block-level journalled filesystem. It could have been based on minixfs, UFS, sysvfs, etc. Or it could have been something altogether new. But I can't think of any benefit in changing the on-disk format from its current ext2ness.
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