Re: [Qemu-devel] [RFC v2 05/15] Make qcow2_open synchronous

[Stefan Hajnoczi]

On Fri, Aug 09, 2013 at 07:43:55PM +0200, Charlie Shepherd wrote:
> +static int qcow2_open(BlockDriverState *bs, QDict *options, int flags)
> +{
> +    Coroutine *co;
> +    struct QOpenCo qo = {
> +        .bs = bs,
> +        .options = options,
> +        .flags = flags,
> +        .ret = NOT_DONE,
> +    };
> +
> +    co = qemu_coroutine_create(qcow2_co_open_entry);
> +    qemu_coroutine_enter(co, &qo);
> +    while (qo.ret == NOT_DONE) {
> +        qemu_aio_wait();
> +    }

I think a cleaner approach is a bool qo.done field instead of using a
magic NOT_DONE value.  This way the return value of qcow2_co_open() can
never collide with NOT_DONE.

(In block.c we use NOT_DONE but I'd like to start using a separate field
to indicate completion in new places.)