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    SubjectRe: [PATCH] deadline io scheduler
    On Mon, Sep 30, 2002 at 10:15:22AM +0200, Jens Axboe wrote:
    > On Thu, Sep 26 2002, Patrick Mansfield wrote:

    > > I haven't look closely at the block tagging, but for the FCP protocol,
    > > there are no tags, just the type of queueing to use (task attributes)
    > > - like ordered, head of queue, untagged, and some others. The tagging
    > > is normally done on the adapter itself (FCP2 protocol AFAIK). Does this
    > > mean block level queued tagging can't help FCP?
    >
    > The generic block level tagging is nothing more than tag management. It
    > can 'tag' a request (assigning it an integer tag), and later let you
    > locate that request by giving it the tag.
    >
    > I suspect you need none of that for FCP. Instead it looks more like you
    > can set the task attributes based on the type of request itself. So you
    > would currently set 'ordered' for a request with REQ_BARRIER set. And
    > you could set 'head of queue' for REQ_URGENT (I'm making this one up
    > :-), etc.
    >
    > Do you need any request management to deal with FCP queueing? It doesn't
    > sound like it.

    No.

    OK I understand it now - if someone wants to put barrier support in an FCP
    adapter driver something like we have in scsi_populate_tag_msg() would be
    useful, an inline or macro like:

    static inline int scsi_is_ordered(Scsi_Cmnd *SCpnt)
    {
    if (SCpnt->request->flags & REQ_BARRIER)
    return 1;
    else
    return 0;
    }

    -- Patrick Mansfield
    -
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