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    SubjectRe: Large File support and blocks.

    On Fri, Sep 01, 2000 at 01:30:26PM +0300, Matti Aarnio wrote:
    > Stephen, could you have a moment to look at the struct buffer_head {}
    > alignment matters ? And possible configure time change to make the
    > block number possibly a 'long long' variable ?

    > Changeing field order might be doable now, while I definitely think that
    > changeing blocknumber variable type is 2.5 matter.

    Right --- 2.5 will have to see a proper API for allowing 64-bit
    addressing on PCI buses too, for large memory Intel boxes. Right now
    we force bounce buffers in the ll_rw_block code, but we need a way to
    push that down to the driver if a given driver can do PCI64 or DAC
    addressing. I'd rather not touch things now, but wait until we're
    ready to do the job properly.

    > opposed by Linus in the past (see <linux/fs.h> for it), putting
    > 64-bit integer in place of 32-bit one grows the head by one
    > extra padding (32 bits) at some architectures in addition to
    > the variable size growth. A "whoops!" I think.
    > I think that for example SPARC32 has stricter alignment rules than
    > what i386 and 68k series processors have.

    The compiler will usually deal with that by adding the necessary
    padding. You need this even on i386 --- ints get 32-bit aligned even
    if preceeded by a char or short type in a struct.

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