Subject: Re: File > 2G on a dvd
To: Rhialto <>
From: Wolfgang Solfrank <>
List: current-users
Date: 11/29/2004 19:25:50

> Not knowing the ins and outs of the filesystem code, I can't think why
> any fs independent code would need a byte offset <-> relative block
> number conversion. Any place where that is seriously used would be
> inside the specific filesystem code itself? Perhaps it won't much matter
> if the naively calculated relative block numbers are only imaginary.
> And perhaps the issues are even smaller because cd9660 is a read-only
> filesystem (although it would be nice if it could be implemented r/w,
> but I'm not sure the specification allows that easily).

Well, there are various things that come into play here.  There actually
_is_ no interface where fs independent code could ask the filesystem what
was the relative block number of some byte offset.  But the buffer cache
is only buffering full blocks, and it is caching those as file relative
blocks, not filesystem relative ones (maybe this has changed with ubc?
probably not much, but I'd have to look), so it does determine the file
relative block number by division of the file offset.

One could probably work around this limitation in the filesystem code,
but that'd need quite a bit of hacking...

ws@TooLs.DE				Wolfgang Solfrank, TooLs GmbH