A few weeks ago, this page looked
at possible additions to the ext3 filesystem
and the question of
whether the time had come to freeze ext3 and put new features into a new
ext4 filesystem again. The ext2/3 filesystem developers have now responded to that discussion
with a clear answer: they will be moving on to ext4.
More specifically, a new filesystem will be created under fs/ext4
in the kernel source. Said filesystem will register itself as
"ext3dev," in an attempt to make it crystal clear that it is a
development filesystem, not suitable for the storage of data which one
actually wishes to keep. New feature work - especially changes which
change on-disk formats and prevent interoperation with current ext3 implementations
- will go into this new filesystem, while ext3 will continue to receive bug
fixes and some safe improvements. Throughout this process, the new
filesystem will retain its ability to work with the current ext3 format.
Sometime in the future, ext3dev will be declared stable and renamed "ext4."
Once the last bugs have been shaken out, this filesystem will lose its
"experimental" designation and users will be encouraged to upgrade. Since
support for ext3 formats will be there, this upgrade should be an easy
process, with no backup-and-restore step or downtime required. Further in
the future, the ext3 code may be removed and ext4 would transparently handle
ext3 filesystems as well.
There seems to be little opposition to this approach, so it would appear
that things will happen this way. Since the addition of a new,
experimental filesystem carries little regression risk, the creation of
ext4 and the addition of some new features (extents, for example) could yet
happen for 2.6.18.
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