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    SubjectRe: [RFC] Union Mount: Readdir approaches
    On Fri, Sep 07, 2007 at 01:28:55PM +0530, Bharata B Rao wrote:
    > On Fri, Sep 07, 2007 at 04:31:26PM +0900, wrote:
    > >
    > > When the first readdir is issued:
    > > - call vfs_readdir for every underlying opened dir (file) object.
    > > - store every entry to either the hash table for the result or the
    > > whiteout, when the same-named entry didn't exist in the tables.
    > > - to improvement the performance, the allocated memory for the hash
    > > tables are managed in a pointer array. and the elements are
    > > concatinated logically by the pointer.
    > > - the pointer for the result-table, the version, and the currect jiffies
    > > are set to vdir, which is a cache in an inode.
    > > - all cache are copied to a member in a file object.
    > > - the index of the cache memory block and the offset in an array is
    > > handled as the seek position.
    > Ok, interesting approach. So you define the seek behaviour on your
    > directory cache rather than allowing the underlying filesystems to
    > interpret the seek. I guess we can do something similar with Union
    > Mounts also.

    Unless I missunderstood something, Unionfs uses the same approach. Even
    Unionfs's ODF branch does the same thing. The major difference is that we
    keep the cache in a file on a disk.

    Josef 'Jeff' Sipek.

    Evolution, n.:
    A hypothetical process whereby infinitely improbable events occur with
    alarming frequency, order arises from chaos, and no one is given credit.
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