Re: qdisk vs. file as vbd type

[Olaf Hering <olaf@aepfle.de>]

On Fri, Jan 10, Ian Campbell wrote:

> On Fri, 2014-01-10 at 15:40 +0100, Olaf Hering wrote:
> > What is the reason the backend 'type' property of a configured disk is
> > now "qdisk" instead of "file"?
> 
> Because qdisk is the backend instead of loop+blk (==file) I think this
> just happens naturally.
> 
> >  Would the guest really care about that
> > detail?  For example block-front currently just checks for "phy" and
> > "file" when deciding if discard should be enabled.
> 
> That sounds entirely bogus, it should be checking for some sort of
> feature-discard.

It does that, then calls blkfront_setup_discard which in turn knows just
about phy and file. And I wonder why it does that.
Maybe this function should be simplified to assume that if its called
feature_discard can be enabled. And if both
discard-granularity/discard-alignment exist those properties should be
assigned, similar for discard-secure.

Now that I look at the history of blkfront_setup_discard:

 Li, Konrad, why does that function care at all about the 'type'?
 Shouldnt that check be removed?

Olaf