Reiser4 Internal Abstraction Layer
The ongoing discussion about the Reiser4 filesystem [story] continues on the lkml. Jeff Garzik discussed the complexity introduced by a plugin layer [story], suggesting it is really a second VFS, "furthermore, it completely changes the notion of what a Linux filesystem is. Currently, each Linux filesystem is a tightly constrained set of metadata support. reiser4 changes 'tightly constrained' to 'infinity'. While that freedom is certainly liberating, it also has obvious support costs due to new admin paradigms and customer configuration possibilities."
Linux creator Linus Torvalds weighed in on the discussion, "as long you call them 'plugins' and treat them as such, I (and I suspect a lot of other people) are totally uninterested, and in fact, a lot of people will suspect that the primary aim is to either subvert the kernel copyright rules, or at best to create a mess of incompatible semantics with no sane overlying rules for locking etc." He went on to add, "as far as I'm concerned, the problem with reiser4 is that it hasn't tried to work with the VFS people.