RE: [PATCH] [RFC] LBD fixes for Linux 2.6.10 [2/2]

["Tony Battersby" <tonyb@cybernetics.com>]

> > 1) Use sector_t rather than long or unsigned long for block numbers.
> > For auditing, just search for all occurrences of "long" in
> the filesystem
> > code and make sure it is not referring to a block number.
>
> That's actually not wise.  For ext3, the block numbers _on disc_
> are 32-bit in size, so making them sector_t in memory is just a waste.
> reiserfs seems to be the same.  OTOH, XFS does use 64-bit
> blocks on disc,
> so should use an explicitly 64-bit size in memory too.

Thanks, that's why I was looking for feedback before going further.  Is
there anywhere in the fs-specific code that deals with real sector
numbers rather than fs block numbers?  Any variable that deals with real
sector numbers should be sector_t, even if the filesystem uses only
32-bit block numbers.  For example, an ext3 filesystem might be created
in the 3-4 TB range of a 4 TB disk, in which case the fs block numbers
fit into a 32-bit quantity but the real sector numbers need to be 64-bit
because of the large starting offset.  If the fs-specific code doesn't
deal with real sector numbers, then there is probably nothing that needs
to be done for ext3 or reiserfs.

Anthony J. Battersby
Cybernetics