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SubjectRe: [CFT] BeFS filesystem 0.6


On Tue, 25 Dec 2001, Will Dyson wrote:

> A & B) I originaly had plans to make the driver work under a variety of
> different VFSs (maybe freebsd and atheos) and to have user-space tools
> (like the old mtools for DOS) for people on other OSs. That was the
> motivation behind those extra abstractions, but I've actually kinda lost
> interest in the idea. I'll just take 'em out if it really offends
> people's asthetic sense. Perhaps kernel drivers just weren't meant to be
> portable.

Well, if you want portable - do it in userland and use CODA...

> B) The PPC and x86 versions of BeOS each write their filesystem metadata
> in native byte-order. So this would only be a problem with disks that
> were formatted on a big-endian system and read on a little-endian (or
> the other way around, of course). I've been meaning to handle that case
> "someday".

Better do it early, while amount of code is not too large. Endian-clean
code is easy. The rule is: never treat any "integer" types from disk as
assignment-compatible with int. Always use something like fs32_to_cpu(),
etc. - it's cleaner that way and inlined functions actually work fine.

> F) Ideally, I would detect both the endianness of the filesystem and the
> host, and refuse to mount if they differ (or byte-swap the metadata).
> Can I rely on #ifdef __LITTLE_ENDIAN to detect the endianness I am
> running on?

See above (and check how sysvfs does it - there it's even more obvious,
since you have to deal with _3_ variants of on-disk bytesex (big-endian,
little-endian and NUXI).

> > befs_count_blocks() also needs cleanup.
>
> How so, please?

Same thing - endianness issues.

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