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Date: Tue, 26 Aug 2014 10:46:36 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [RFC PATCH v2 6/8] dma: Implement .cancel_async
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To: Fam Zheng <famz@redhat.com>, qemu-devel@nongnu.org
Cc: Kevin Wolf <kwolf@redhat.com>, Stefan Hajnoczi <stefanha@redhat.com>

Il 26/08/2014 08:08, Fam Zheng ha scritto:
> +    if (dbs->cancelled) {
> +        ret = -ECANCELED;
> +    }

Why is dbs->cancelled necessary?

>      dma_bdrv_unmap(dbs);
>      if (dbs->common.cb) {
>          dbs->common.cb(dbs->common.opaque, ret);
> @@ -141,6 +148,9 @@ static void dma_bdrv_cb(void *opaque, int ret)
>  
>      trace_dma_bdrv_cb(dbs, ret);
>  
> +    if (dbs->cancelled) {
> +        ret = -ECANCELED;
> +    }
>      dbs->acb = NULL;
>      dbs->sector_num += dbs->iov.size / 512;
>  
> @@ -185,6 +195,7 @@ static void dma_aio_cancel(BlockDriverAIOCB *acb)
>  
>      trace_dma_aio_cancel(dbs);
>  
> +    dbs->cancelled = true;
>      if (dbs->acb) {
>          BlockDriverAIOCB *acb = dbs->acb;
>          dbs->acb = NULL;
> @@ -196,9 +207,25 @@ static void dma_aio_cancel(BlockDriverAIOCB *acb)
>      dma_complete(dbs, 0);
>  }
>  
> +static void dma_aio_cancel_async(BlockDriverAIOCB *acb)
> +{
> +    DMAAIOCB *dbs = container_of(acb, DMAAIOCB, common);
> +
> +    trace_dma_aio_cancel(dbs);
> +
> +    dbs->cancelled = true;
> +    if (dbs->acb) {
> +        acb = dbs->acb;
> +        dbs->acb = NULL;

Why do you need to set dbs->acb to NULL, since the callback is going to
be called?

Paolo

> +        bdrv_aio_cancel_async(acb);
> +    }
> +}