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    SubjectRe: udev and devfs - The final word
    On Dec 31, 2003  22:55 +0000, viro@parcelfarce.linux.theplanet.co.uk wrote:
    > h) nfsd uses device number as a substitute for export ID if said
    > ID is not given explicitly. That, BTW, is a big problem for crackpipe
    > dreams about random device numbers - export ID _must_ be stable across
    > reboots.

    We had a problem with this and Lustre, when we NFS export it. Lustre is
    already a network filesystem so we don't have a device number. I had a
    discussion with Neil Brown about this and suggested that we allow NFS to
    get a _real_ stable export ID from the filesystem (e.g. superblock UUID
    or similar) instead of the device number hackery which only has a vague
    relationship to stable.

    We implemented it for Lustre with a filesystem option FS_NFSEXP_FSID
    that tells nfsd it can export such a filesystem in the absence of
    FS_REQUIRES_DEV and then put our export ID into sb->s_dev (although I'd
    prefer something slightly cleaner than that).

    Cheers, Andreas
    --
    Andreas Dilger
    http://sourceforge.net/projects/ext2resize/
    http://www-mddsp.enel.ucalgary.ca/People/adilger/

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