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

[Stefano Stabellini]

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 <address@hidden>
> 
> --- 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.