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    SubjectRe: Implementing Meta File information in Linux (and a note at the end on current reiserfs status)
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    In message <Pine.GSO.4.02A.9809021631240.15750-100000@red.seas.upenn.edu>, 
    Vlad
    imir Dergachev writes:
    +-----
    | databases. In fact, /etc/passwd is nothing else but a database, though
    | one wasn't concerned very much with perfomance of it. GUI stuff is
    +--->8

    *cough* *choke* *gasp* Andrew cluster *splutter*

    I suspect Ted could make a similar remark with respect to MIT... then again,
    probably not. (HESIOD?) (I've yet to figure out why CMU thinks that local
    password files are a good thing....)

    | One could also envision the file itself being associated with database
    | entries. In this context the copying of the file will copy the entries
    | as well. If one would attempt to copy the file outside of ext2 that should
    | produce those ".fork" database files.
    +--->8

    One thought I had was that read() on a file with metadata returns a
    structured file containing all the data and metadata *unless* the program
    issues an fcntl() to switch to metadata mode. (Note that metadata/"forks"
    and databases are not disjoint --- Mac System 6 and later, IIRC, use a btree
    for the resource fork.) Having done that, read() returns only normal data
    and other fcntl() operations are used to access metadata.

    If you hide the fcntl()s and metadata-aware read() inside other functions,
    you also get an API which could be implemented as a library on systems
    lacking metadata (the physical disk file actually is the above structured
    file) --- and to provide cross-platform metadata routines for Mac, NTFS,
    OS/2, etc. Of course, at this point the claim could be made that one
    doesn't need the fcntl() stuff, just the library (but! it will perform
    horribly unless the "structured file" is really a file and a backing (e.g.)
    reiserfs directory --- in which case you can lose by not realing that you
    need to copy the directory as well as the file.

    --
    brandon s. allbery [os/2][linux][solaris][japh] allbery@kf8nh.apk.net
    system administrator [WAY too many hats] allbery@ece.cmu.edu
    electrical and computer engineering KF8NH
    carnegie mellon university



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