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Date: Thu, 29 Aug 2013 14:29:22 +0200
From: Stefan Hajnoczi <stefanha@gmail.com>
Message-ID: <20130829122922.GB17744@stefanha-thinkpad.redhat.com>
References: <1376070245-22557-1-git-send-email-charlie@ctshepherd.com>
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In-Reply-To: <1376070245-22557-5-git-send-email-charlie@ctshepherd.com>
Subject: Re: [Qemu-devel] [RFC v2 05/15] Make qcow2_open synchronous
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To: Charlie Shepherd <charlie@ctshepherd.com>
Cc: kwolf@redhat.com, pbonzini@redhat.com, gabriel@kerneis.info, qemu-devel@nongnu.org

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.)