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    SubjectRe: [Ext2-devel] [PATCH 2/9] sector_t format string
    On Wed, Aug 09, 2006 at 11:40:19PM -0700, Andrew Morton wrote:
    > On Wed, 09 Aug 2006 18:20:43 -0700
    > Mingming Cao <> wrote:
    > >
    > > Define SECTOR_FMT to print sector_t in proper format
    > >
    > > ...
    > >
    > > #define HAVE_SECTOR_T
    > > typedef u64 sector_t;
    > > +#define SECTOR_FMT "%llu"
    > We've thus-far avoided doing this. In fact a similar construct in
    > device-mapper was recently removed.
    > Unlike many other attempts, this one appears to be correct (people usually
    > get powerpc wrong, due to its u64=unsigned long).
    > That being said, I'm not really sure we want to add this. It produces
    > rather nasty-looking source code and thus far we've just used %llu and we've
    > typecasted the sector_t to `unsigned long long'. That happens in a lot of
    > places in the kernel and perhaps we don't want to start innovating in ext4
    > ;)
    > That also being said... does a 32-bit sector_t make any sense on a
    > 48-bit-blocknumber filesystem? I'd have thought that we'd just make ext4
    > depend on 64-bit sector_t and be done with it.

    Ext4 will support a 48-bit blocknumber format for extents, but I do
    want to make ext4 suitable as a general purpose filesystem, and 32-bit
    systems will be around for I fear far longer than people might wish.
    So while I agree that we shouldn't go _too_ far out of our way to make
    things efficient on 32-bit systems, if it's not that much work to
    support a 32-bit sector_t, we ought to do it.

    So how about a compromise? We allow for a 32-bit sector_t in ext4,
    but we drop the SECTOR_FMT, and rely on %llu and typecasts in
    printk's. Then the only other extra hair in the filesystem code will
    be a mount-time check to make sure we don't try to mount a large
    filesystem on system with a 32-bit sector_t.

    - Ted
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