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    SubjectRe: [PATCH] Block layer: separate out queue-oriented ioctls
    On Mon, 19 Feb 2007, Douglas Gilbert wrote:

    > Alan,
    > The SG_GET_RESERVED_SIZE ioctl is also defined in
    > the block layer, see block/scsi_ioctl.c .

    Ah, I didn't know that. (Or more likely, I used to know and have since
    forgotten.) Thanks for pointing it out.

    > I suspect it is just a kludge to fool cdrecord that it
    > is talking to a sg device. [One of many kludges in the
    > block SG_IO ioctl implementation to that end.]
    > So perhaps the block layer versions of SG_SET_RESERVED_SIZE
    > and SG_GET_RESERVED_SIZE need to be similarly capped.

    Yes. In fact one of them already is, but the other should be too.

    > Actually I think that I would default SG_GET_RESERVED_SIZE to
    > request_queue->max_sectors * 512 in the block layer
    > implementation (as there is no "reserve buffer" associated
    > with a block device).


    Come to think of it, the reserved_size value used when a new sg device is
    created should also be capped at max_sectors * 512. Agreed? I can't see
    any reason for ever having a larger buffer -- it would be impossible to
    make use of the extra space.

    Alan Stern

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      Last update: 2007-02-20 04:51    [W:0.019 / U:18.836 seconds]
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