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    SubjectRe: [PATCH] UBIFS: fill f_fsid
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    On Mon, 2008-09-01 at 14:16 +0300, Artem Bityutskiy wrote:
    > On Mon, 2008-09-01 at 10:43 +0100, David Woodhouse wrote:
    > > > UBIFS stores 16-bit UUID in the superblock, and it is a good
    > > > idea to return part of it in 'f_fsid' filed of kstatfs structure.
    > >
    > > I think you mean a 16-byte UUID, not 16-bit?
    >
    > Oh, right.
    >
    > >
    > > > + memcpy(&buf->f_fsid, c->uuid, sizeof(__kernel_fsid_t));
    > >
    > > For btrfs I xor the first 64 bits with the second 64 bits, and put
    > > _that_ into f_fsid. You're just putting the first 64 bits in and
    > > ignoring the second 64 bits. Neither is really _better_ than the other;
    > > you just alter the circumstances in which you get collisions. But I
    > > suppose we might as well be consistent about how we do it?
    >
    > Well, xor-ing should not make the random UUID more random, but for
    > consistency purposes sure, I may use xor as well.
    >
    > > Alternatively, there's space in the struct statfs to export a couple
    > > more uint32_ts, and thus the _whole_ of the uuid. Perhaps we should do
    > > that?
    >
    > You mean f_spare? I do not think any application would use it so I doubt
    > it is good idea to use it.

    Well, it wouldn't be called f_spare any more, and applications would
    know that it contains the rest of the UUID if it's non-zero.

    I'd fix nfsd to fix it immediately (like as I just fixed nfsd to use the
    first 64 bits of f_fsid when it's non-zero).

    --
    David Woodhouse Open Source Technology Centre
    David.Woodhouse@intel.com Intel Corporation





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