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    SubjectRe: Loop Encryption
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    > P.S. Is it me, or is get_request() in drivers/block/ll_rw_blk.c
    > particularly complex for the simple job it does (with interrupts
    > disabled I might add)?

    I just rewrote it. It now allocates WRITEs from one end, and READs
    from the other. It is faster - on average, fewer requests are searched.
    Is is also more fair - READs and WRITEs get clustered at the ends
    of the all_requests array, so a READ (higher priority) is less likely
    to fill up a WRITE (lower priority) slot, except when the system is
    busy with lots of requests.

    I also rewrote get_request_wait() and eliminated __get_request_wait().
    The new code has generic support for handling drivers (like loop)
    that require multiple requests to complete a single request. They
    are put to sleep BEFORE THEY CAN START until there are enough free
    requests - the old code could only do this for single requests.

    I've been punishing the code for over 4 hours continuously now,
    by moving an 8 MB file to/from a deeply looped (XOR) file
    (mounted=loop7->loop6->loop5->loop4->loop3->loop2->loop1->loop0->file)
    and syncing. Works wonderfully.

    The source is not yet ready for prime time (I know I can make it better),
    but it is available directly from me as part of my modular loop driver
    patch (which now supports kerneld too!).

    After this, I attack the buffer cache (particularly bdflush) to improve
    its loop driver support.

    --
    Andrew E. Mileski mailto:aem@netcom.ca
    Linux Plug-and-Play Hardware Support http://www.redhat.com/linux-info/pnp/
    XFree86 Matrox Team http://www.bf.rmit.edu.au/~ajv/xf86-matrox.html
    Ottawa-Carleton Linux User's Group (OCLUG) http://www.storm.ca/~linux/

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