Hi Pete,
On Tue, 11 Dec 2007 15:48:03 -0800, Pete Zaitcev <zaitcev@xxxxxxxxxx> wrote:
> > if (scsi_status == 0) {
> > - uptodate = 1;
> > + error = 0;
> > } else {
> > - uptodate = 0;
> > + error = -EIO;
> > rq->errors = scsi_status;
> > }
> > - end_that_request_first(rq, uptodate, rq->hard_nr_sectors);
> > - end_that_request_last(rq, uptodate);
> > + if (__blk_end_request(rq, error, blk_rq_bytes(rq)))
> > + BUG();
>
> Acked-by: Pete Zaitcev <zaitcev@xxxxxxxxxx>
>
> I follow the discussion, actually, and wanted to ask someone to look
> closer if it's appropriate to use __blk_end_request() here.
> My understanding was, blk_end_request() is the same thing, only
> takes the queue lock. But then, should I refactor ub so that it
> calls __blk_end_request if request function ends with an error
> and blk_end_request if the end-of-IO even is processed? If not,
> and the above is sufficient, why have blk_end_request at all?
The difference between blk_end_request() and __blk_end_request() is
whether the queue lock is held or not when end_that_request_last()
is called.
It's not relevant to the status of the request (error or not).
I'm using __blk_end_request() here and I think it's sufficient, because:
o end_that_request_last() must be called with the queue lock held
o ub_end_rq() calls end_that_request_last() without taking
the queue lock in itself.
So the queue lock must have been taken outside ub_end_rq().
But, if ub is calling end_that_request_last() without the queue lock,
it is a bug in the original code and we should use blk_end_request()
to fix that.
Does that answer satisfy you?
Thanks,
Kiyoshi Ueda
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