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Date: Mon, 9 Nov 2015 17:38:36 +0800
From: Fam Zheng <famz@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v3 8/9] block: Introduce
	BlockDriver.bdrv_drain callback
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Stefan Hajnoczi <stefanha@redhat.com>, qemu-block@nongnu.org, Peter Lieven <pl@kamp.de>, qemu-devel@nongnu.org, Ronnie Sahlberg <ronniesahlberg@gmail.com>

On Mon, 11/09 10:24, Paolo Bonzini wrote:
> 
> 
> On 09/11/2015 03:56, Fam Zheng wrote:
> > +    if (bs->drv && bs->drv->bdrv_drain) {
> > +        bs->drv->bdrv_drain(bs);
> > +    }
> > +    QLIST_FOREACH(child, &bs->children, next) {
> > +        BlockDriverState *cbs = child->bs;
> > +        if (cbs->drv && cbs->drv->bdrv_drain) {
> > +            cbs->drv->bdrv_drain(bs);
> > +        }
> > +    }
> 
> I think this is not enough, because the children could have children as
> well.
> 
> Perhaps you can do it like bdrv_flush: one function does the call to
> bdrv_drain and the recursion on children; bdrv_drain calls that one
> function and then does the "while (busy)" loop.
> 

Right, this function is no longer recursive and only goes to one layer down.

Will fix.

Thanks,

Fam