Re: [Xen-devel] qemu/xendisk: properly update stats in ioreq_release()

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Mon, 14 May 2012, Jan Beulich wrote:
> >>> On 11.05.12 at 18:01, Stefano Stabellini 
> >>> <stefano.stabellini@xxxxxxxxxxxxx>
> wrote:
> > On Thu, 10 May 2012, Jan Beulich wrote:
> >> While for the "normal" case (called from blk_send_response_all())
> >> decrementing requests_finished is correct, doing so in the parse error
> >> case is wrong; requests_inflight needs to be decremented instead.
> >> 
> >> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> >> 
> >> --- a/hw/xen_disk.c
> >> +++ b/hw/xen_disk.c
> >> @@ -154,7 +154,7 @@ static void ioreq_finish(struct ioreq *i
> >>      blkdev->requests_finished++;
> >>  }
> >>  
> >> -static void ioreq_release(struct ioreq *ioreq)
> >> +static void ioreq_release(struct ioreq *ioreq, bool finish)
> >>  {
> >>      struct XenBlkDev *blkdev = ioreq->blkdev;
> >>  
> >> @@ -162,7 +162,10 @@ static void ioreq_release(struct ioreq *
> >>      memset(ioreq, 0, sizeof(*ioreq));
> >>      ioreq->blkdev = blkdev;
> >>      QLIST_INSERT_HEAD(&blkdev->freelist, ioreq, list);
> >> -    blkdev->requests_finished--;
> >> +    if (finish)
> >> +        blkdev->requests_finished--;
> >> +    else
> >> +        blkdev->requests_inflight--;
> >>  }
> >>  
> >>  /*
> >> @@ -449,7 +452,7 @@ static void blk_send_response_all(struct
> >>      while (!QLIST_EMPTY(&blkdev->finished)) {
> >>          ioreq = QLIST_FIRST(&blkdev->finished);
> >>          send_notify += blk_send_response_one(ioreq);
> >> -        ioreq_release(ioreq);
> >> +        ioreq_release(ioreq, true);
> >>      }
> >>      if (send_notify) {
> >>          xen_be_send_notify(&blkdev->xendev);
> >> @@ -505,7 +508,7 @@ static void blk_handle_requests(struct X
> >>              if (blk_send_response_one(ioreq)) {
> >>                  xen_be_send_notify(&blkdev->xendev);
> >>              }
> >> -            ioreq_release(ioreq);
> >> +            ioreq_release(ioreq, false);
> >>              continue;
> >>          }
> > 
> > In case of an error returned by ioreq_parse requests_finished should
> > also be decremented.
> 
> I don't think so - it gets incremented in ioreq_finish(), and that gets
> called only when I/O was at least attempted (which isn't the case
> when parse failed).

You are right, the patch is correct as it is.
However it is not following QEMU's CODING_STYLE (braces around single
line statements): you can use scripts/checkpatch.pl to check your
patches for code style errors.

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