CC'ing the Unionfs list.
In message <[EMAIL PROTECTED]>, Michael Halcrow writes:
>
> Since Unionfs is in plan for sending up to the LKML, I can imagine the
> Linux kernel community being all the more insistent that Christoph's
> suggestion be acted upon.
>
> What components of Unionfs and eCryptfs can be abstracted into
> something like fs/stackfs/?
>
> Thanks,
> Mike
>
> ----- Forwarded message from Christoph Hellwig <[EMAIL PROTECTED]> -----
>
> =46rom: Christoph Hellwig <[EMAIL PROTECTED]>
> Subject: Re: [PATCH 0/13: eCryptfs] eCryptfs Patch Set
>
> - please split all the generic stackable filesystem passthorugh routines
> into a separated stackfs layer, in a few files in fs/stackfs/ that
> you depend on. They'll get _GPL exported to all possible stackable
> filesystem. They'll need their own store underlying object helpers,
> but that can be made to work by embedding the generic stackfs data
> as first thing in the ecryptfs object.
>
> ----- End forwarded message -----
Mike, that's a good idea: one I've always wanted to do.
But I think we should coordinate our efforts on this very carefully. (I've
done a "few" stackable file systems. :-) Seriously, we need to ensure that
whatever gets abstracted will work for all future stacked file systems:
including size-changing ones such as gzipfs, and fanout ones such as
unionfs.
Alas, I think it's going to be hard to find common pass-through functions b/t
unionfs and ecryptfs. Unionfs's fanout nature means that the pass-through
has to be iterated over N branches below; that iteration happens mostly
inside various methods (e.g., in deep "for" loops).
My suggestion is this. Let's keep the discussions for now on the fistgen
list. Why don't you first start by analyzing ecryptfs's code and propose
how you'd separate stackfs from the core ecryptfs. Don't actually do the
work, just propose it in an email. Then, we'll review it and see how it
relates to other stackable file systems, esp. unionfs. (BTW, I'm sure that
stackfs itself will morph and grow over time.)
BTW, I strongly suggest you first read our article "On Incremental File
System Development", found here
http://www.fsl.cs.sunysb.edu/all-pubs.html#tos-zen
It'll tell you a lot about what kinds of facilities stackable file systems
may want in a generic manner.
Cheers,
Erez.
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