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    SubjectRe: [RFC][PATCH 0/2]Extend ext3 filesystem limit from 8TB to 16TB
    On Mar 29, 2006  17:38 -0800, Mingming Cao wrote:
    > There are places in ext3 code to use "int" to represent block numbers in
    > kernel(not on-disk). This seems the "only" reason that why we can only
    > have 8TB ext3 rather than 16TB. Most times it just a bug with no
    > particular reason why not use unsigned 32 bit value, so the fix is easy.
    > However, it is not so straightforward fix for the ext3 block allocation
    > code, as ext3_new_block() returns a block number, and "-1" to indicating
    > block allocation failure. Ext3 block reservation code, called by
    > ext3_new_block(), thus also use "int" for block numbers in some places.

    What might make the code a lot clearer, easier to audit, and easier to
    fix in the future is to declare new types for fs block offsets and group
    block offsets. Something like "ext3_fsblk" and "ext3_grblk". That way,
    we can declare ext3_fsblk as "unsigned long" and "ext3_grblk" as "unsigned
    int", and we could optionally change ext3_fsblk to be "unsigned long long"
    later to support 64-bit filesystems without having to re-patch all of the

    It would be more clear what type of block offset a function is handling
    (fs-wide or group-relative). If we wanted to be able to overload the
    block number with an error code we could use ERR_PTR and PTR_ERR like
    macros, and just restrict the filesystem to 2^32 - 1024 blocks until we
    extend it to 64 bits.

    Cheers, Andreas
    Andreas Dilger
    Principal Software Engineer
    Cluster File Systems, Inc.

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      Last update: 2006-03-30 19:39    [W:0.022 / U:95.868 seconds]
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