On Fri, 12/18 07:05, Paolo Bonzini wrote:
>
>
> On 18/12/2015 01:57, Fam Zheng wrote:
> > Oh hang on, in scsi_req_dequeue, if req->enqueued is already false, the
> > matching scsi_req_unref is never called.
>
> The matching unref for scsi_req_cancel_async's ref is in
> scsi_req_cancel_complete. You're right that there is a leak if
> we get to the second cancellation with req->aiocb, and we should
> never get there with !req->aiocb. So the patch is wrong, but
> we should add some documentation instead of plainly reverting it:
>
> diff --git a/hw/scsi/scsi-bus.c b/hw/scsi/scsi-bus.c
> index 00bddc9..378bf4d 100644
> --- a/hw/scsi/scsi-bus.c
> +++ b/hw/scsi/scsi-bus.c
> @@ -1759,6 +1759,17 @@ void scsi_req_cancel_async(SCSIRequest *req, Notifier
> *notifier)
> if (notifier) {
> notifier_list_add(&req->cancel_notifiers, notifier);
> }
> + if (req->io_canceled) {
> + /* Canceling a second time after scsi_req_cancel_complete
> + * is a programming error, hence a blk_aio_cancel_async is
> + * pending; when it finishes, scsi_req_cancel_complete
> + * will be called and will call the notifier we just
> + * added. Just wait for that.
> + */
> + assert(req->aiocb);
> + return;
> + }
> + /* Dropped in scsi_req_cancel_complete. */
> scsi_req_ref(req);
> scsi_req_dequeue(req);
> req->io_canceled = true;
> @@ -1775,6 +1784,8 @@ void scsi_req_cancel(SCSIRequest *req)
> if (!req->enqueued) {
> return;
> }
> + assert(!req->io_canceled);
> + /* Dropped in scsi_req_cancel_complete. */
> scsi_req_ref(req);
> scsi_req_dequeue(req);
> req->io_canceled = true;
>
> Does this look sane?
>
Yes, it looks correct to me.
Fam
