ideas about a unioning file system
ezk at cs.sunysb.edu
Fri Jun 20 09:57:32 PDT 2003
In message <3EF31B05.5070004 at tenebras.com>, Michael Sierchio writes:
> Poul-Henning Kamp wrote:
> > The majority of the problems we have in this area can be nailed down
> > to only two issues:
> > 1. The very tricky semantics of rename(2)
> > 2. read/write/mmap coherency for stacked filesystems.
> This is of particular interest to me. While Poul-Henning has
> done some very interesting work on encryption at the GEOM
> level, I'm trying to work with ACL filesystems and stacking
> crypto filesystems that manage keys with one per file.
Yup, coherency is certainly a difficult problem. We have only begun to look
at it, and implemented some simple solutions (for NCryptfs). We'll be
exploring something more like Heidemann's work (SOSP'95) in the future.
> Imagine the coherency problems when pages don't match up
> because of IVs for CBC block mode encryption, and imagine
> the headache for (un-)locking pages at different levels.
Those of you doing crypto f/s, might be interested in reading our
paper on NCryptfs, which was just presented at Usenix:
> Making it easy for FIST and cryptfs (Erez Zadok's stuff) would
> be very helpful. (I.e. gee, I'd rather not have to do this
> on Linux).
BTW, we've completed a port of the fist templates to 4.x (all versions) and
5.0. We're planning to release a new fistgen RSN.
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