Re: [Qemu-devel] [PATCH v2] support add-cow format

[Paolo Bonzini]

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