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Date: Fri, 22 Aug 2014 17:37:58 +0800
From: Fam Zheng <famz@redhat.com>
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Subject: Re: [Qemu-devel] [RFC PATCH 1/9] block: Add bdrv_aio_cancel_async
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>, qemu-devel@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>

On Fri, 08/22 10:14, Paolo Bonzini wrote:
> Il 22/08/2014 03:23, Fam Zheng ha scritto:
> > What about we save cb and opaque locally, and set acb->cb to a nop. When cancel
> > is done we can call the original cb?
> 
> That might work but needs some auditing.  Right now the AIOCB is still
> valid when the callback is called, and this would be changed.
> 
> Also, having different semantics for cancellation vs. completion would
> be painful.
> 

Exactly. I'd rather not change the contract then.

Alternatively, we may add a refcnt field to BlockDriverAioCB and grab one before
calling .cancel, so the qemu_aio_release will not free it.

Fam