Re: [Qemu-devel] [PATCH] scsi: always call notifier on async cancellation

[Fam Zheng <famz@redhat.com>]

On Wed, 12/16 19:33, Paolo Bonzini wrote:
> This was found by code inspection.  If the request is cancelled twice,
> the notifier is never called on the second cancellation request,
> and hence for example a TMF might never finish.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  hw/scsi/scsi-bus.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/hw/scsi/scsi-bus.c b/hw/scsi/scsi-bus.c
> index 524a998..4c121fe 100644
> --- a/hw/scsi/scsi-bus.c
> +++ b/hw/scsi/scsi-bus.c
> @@ -1759,9 +1759,6 @@ void scsi_req_cancel_async(SCSIRequest *req, Notifier *notifier)
>      if (notifier) {
>          notifier_list_add(&req->cancel_notifiers, notifier);
>      }
> -    if (req->io_canceled) {
> -        return;
> -    }
>      scsi_req_ref(req);
>      scsi_req_dequeue(req);
>      req->io_canceled = true;
       if (req->aiocb) {
           blk_aio_cancel_async(req->aiocb);
       } else {
           scsi_req_cancel_complete(req);
       }

A second TMF must be blk_aio_cancel_async case, otherwise the first one would
have already completed the request synchronously in scsi_req_cancel_complete.
With that in mind, I think returning early is not a problem. But I suppose
these are also idempotent so this change is not breaking anything, either.

Fam