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    SubjectRe: blocks or KB? (was: .. current meaning of blk_size array)
    At 05:55 15/11/01, Andreas Dilger wrote:
    >On Nov 15, 2001 00:34 -0500, William Park wrote:
    > > Judging by 'driver/block/nbd.c', it counts by BLOCK_SIZE=1204
    > > (BLOCK_SIZE_BITS=10), even though you can set the block size to
    > > [512,1024,...,PAGE_SIZE=4096]. Since NBD counts this 1KB block using
    > > 'u64' integer, the ultimate size of filesystem is determined by the
    > > kernel block device support.
    > >
    > > Looking at 'fs/block_dev.c', you can set the block size to
    > > [512,1024,...,PAGE_SIZE=4096] also. But, 'max_block()' returns block
    > > count in whatever block size of the device, not in BLOCK_SIZE:
    >
    >Sadly, while you _might_ be able to change the BLOCK_SIZE to be something
    >other than 1kB, there are probably so many places that assume a 1kB size
    >that you will need a lot of fixing. I'm not saying that fixing these
    >things is bad (it would actually be good for many reasons), but just a
    >heads-up that changing the BLOCK_SIZE define _probably_ won't get you 8TB
    >devices (maybe a broken system, or corrupt fs instead). Use caution.

    I changed BLOCK_SIZE back in the 2.4.0-test8 to 512 and had to do some
    modifications to drivers/ide, drivers/scsi, fs/partitions and to fs/ext2 to
    get it to work (patch is 10kiB so not too bad but it doesn't deal with the
    MD driver nor with any of the devices/fs I don't actually use). It then
    worked nicely for me. (Only minor problem with floppy disk resulting in a
    block size error from ll_rw_block but it always went ahead and worked after
    outputting the error.)

    And yes, the fixes needed are mostly because of assumptions about
    BLOCK_SIZE being 1024 bytes... If anyone is interested in having a look,
    the now outdated patch is available on the web:

    http://www-stu.christs.cam.ac.uk/~aia21/linux/blksize512.patch

    Anton


    --
    "I've not lost my mind. It's backed up on tape somewhere." - Unknown
    --
    Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @)
    Linux NTFS Maintainer / WWW: http://linux-ntfs.sf.net/
    ICQ: 8561279 / WWW: http://www-stu.christs.cam.ac.uk/~aia21/

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