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Date: Fri, 23 Sep 2011 15:49:16 +0200
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Subject: Re: [Qemu-devel] [PATCH v2] support add-cow format
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To: Kevin Wolf <kwolf@redhat.com>
Cc: wdongxu@cn.ibm.com, Dong Xu Wang <wdongxu@linux.vnet.ibm.com>, qemu-devel@nongnu.org, stefanha@linux.vnet.ibm.com

On 09/23/2011 02:20 PM, Kevin Wolf wrote:
>> +static BlockDriverAIOCB *add_cow_aio_flush(BlockDriverState *bs,
>> +        BlockDriverCompletionFunc *cb, void *opaque)
>> +{
>> +    BDRVAddCowState *state = bs->opaque;
>> +    bdrv_aio_flush(state->image_hd, cb, opaque);
>> +    return bdrv_aio_flush(bs->file, cb, opaque);
>
> This will invoke the callback twice, and opaque will probably be invalid
> after the first callback. Not good.
>
> This code is also lacking error handling for the ifrst bdrv_aio_flush.

I'll repost the NBD series today, so that Dong Xu Wang can implement 
this as co_flush.

Paolo