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SubjectRe: Block sizes < 512 bytes
On Mon, 6 Sep 1999, Robert Norris wrote:

> Greetings.
>
> I've been working on a filesystem driver for old CBM1541 disks (and images),
> mainly because I have a collection of some 3000+ disks.

Hmmm. I'll send you CBMFS right away... :^) (Original version for v2.0
kernels written by Dan Fandrich, I adapted it to v2.2 kernels and made it
possible to built into the kernel)

> Tthe filesystem on these disks is structured into 683 blocks of 256 bytes
> each. The 'superblock' is on block 358.

CBMFS solves this by combining 2 blocks into one.

> In my first attempt, part of the code in read_super() looked like this:
>
> set_blocksize(s->s_dev, 256);
> bh = bread(s->s_dev, 258, 256);
>
> After testing and enjoying the panic that ensued, I did some hunting and
> discovered in fs/buffer.c that the block size must >= 512 bytes.
>
> Why is this? I admit I'm unfamiliar with most of the filesystem code, but
> it seems a little silly to limit the block size in this (seemingly
> arbitrary) way.
>
> Am I doing this wrong? Is there another way to acheive what I want?

See above. I'm working on 1571 support right now, as well as R/W support.
Maybe we can cooperate in some way.

/David Weinehall
_ _
// David Weinehall <tao@acc.umu.se> /> Northern lights wander \\
// Project MCA Linux hacker // Dance across the winter sky //
\> http://www.acc.umu.se/~tao/ </ Full colour fire </


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