On Thu, Aug 21, 2014 at 07:56:51PM +0800, Fam Zheng wrote:
> @@ -110,6 +109,22 @@ static void qemu_laio_completion_cb(EventNotifier *e)
> }
> }
>
> +static void laio_cancel_async(BlockDriverAIOCB *blockacb)
> +{
> + struct qemu_laiocb *laiocb = (struct qemu_laiocb *)blockacb;
> + struct io_event event;
> + int ret;
> +
> + ret = io_cancel(laiocb->ctx->ctx, &laiocb->iocb, &event);
> + laiocb->ret = -ECANCELED;
> + if (!ret) {
> + /* iocb is not cancelled, cb will be called by the event loop later
> */
> + return;
> + }No callback will be invoked if io_cancel(2) every cancels the request immediately. The current kernel implementation always returns -EINPROGRESS or some of other error value. But some day it might return 0 and this would leak the request! > + > + laiocb->common.cb(laiocb->common.opaque, laiocb->ret); > +} It would be cleaner to reuse laio_cancel_async() from laio_cancel() to avoid code duplication. For example, there is a useful comment in laio_cancel() explaining that io_cancel(2) doesn't cancel I/O in practice on 2.6.31 era kernels.
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