FreeLists / openbeosstorage / [openbeosstorage] Re: Amiga RDB

["Axel Dörfler" <axeld@xxxxxxxxxxxxxxxx>]

"Ingo Weinhold" <bonefish@xxxxxxxxxxxxxxx> wrote:
> > I am not yet sure how to handle the real partition size - I'll have 
> > a 
> > deeper look at Amiga FFS though, and then I might know. Right now, 
> > I 
> > would think that it's best to simply let the file system decide 
> > what to
> > do with this extra space; at least it looks like the contents 
> > differ on
> > different file systems - that means, that the partition would span 
> > the
> > whole space including the reserved areas.
> > It would just be nice if the file system could access the space 
> > information, though.
> Mmh, we have rather few options: We publish a device for the 
> partition 
> that either includes the reserved space or that doesn't. Unless I 
> miss 
> something, Linux has exactly the same options for its /dev/hdaN. If 
> your observation is correct, then those partitions include the 
> reserved 
> part. I find this not nice, because that means, the file systems must 
> be aware of the underlying partitioning system. Not that this was a 
> problem for us...

It could also just assume always 2 blocks and ignore that number 
completely. That is, the AmigaFFS handler would not use those 2 blocks 
for anything else, but all other file systems would.
BTW the "disk_environment" structure which contains the reserved blocks 
information also contains the block size used for the file system - so 
the file system should have access to that information in anyway.
How do we want to do this? The easiest way would be to reserve some 
keywords for the driver_settings structure. That is, the file system 
gets something like "block_size = 512; reserved_blocks_at_start = 2;" 
added to the standard parameter string. Of course, that is dangerous 
information, but does anybody has a better idea?
We could even have a prefix for them that is filtered out when coming 
from userland (like "_system_").

Adios...
   Axel.