Re: [Qemu-devel] [RFC PATCH 1/9] block: Add bdrv_aio_cancel_async

From: Stefan Hajnoczi <stefanha@redhat.com>
To: Fam Zheng <famz@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [RFC PATCH 1/9] block: Add bdrv_aio_cancel_async
Date: Thu, 21 Aug 2014 14:44:58 +0100	[thread overview]
Message-ID: <20140821134458.GC22844@stefanha-thinkpad.redhat.com> (raw)
In-Reply-To: <1408622216-9578-2-git-send-email-famz@redhat.com>

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On Thu, Aug 21, 2014 at 07:56:48PM +0800, Fam Zheng wrote:
> +/* Async version of aio cancel. The caller is not blocked if the acb implements
> + * cancel_async, otherwise fall back to bdrv_aio_cancel. In both cases, acb->cb
> + * is guarenteed to be called, before or after function returns. */
> +void bdrv_aio_cancel_async(BlockDriverAIOCB *acb)
> +{
> +    if (acb->aiocb_info->cancel_async) {
> +        acb->aiocb_info->cancel_async(acb);
> +    } else {
> +        BlockDriverAIOCB *save = g_new(BlockDriverAIOCB, 1);

Please don't create a dummy BlockDriverAIOCB.  It makes the code
confusing because all other BlockDriverAIOCBs in QEMU are allocated with
qemu_aio_get() and behave in a certain way.

This is not really a BlockDriverAIOCB, it's just a struct to stash the
old cb/opaque in.

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