Messages in this thread | | | Date | Mon, 30 Sep 2002 08:39:54 -0700 | From | Patrick Mansfield <> | Subject | Re: [PATCH] deadline io scheduler |
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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; }
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