[Qemu-devel] Re: [PATCH 2/3] block-nbd: fix use of protocols in backing files and nbd probing

[Anthony Liguori]

On 09/16/2010 03:08 AM, Kevin Wolf wrote:
> Am 11.09.2010 16:04, schrieb Anthony Liguori:
>    
> > The use of protocols in backing_files is currently broken because of some
> > checks for adjusting relative pathnames.
> >
> > Additionally, there's a spurious read when using an nbd protocol that can be
> > quite destructive when using copy-on-read.  Potentially, this can lead to
> > probing an image file over top of NBD but this is completely wrong as NBD
> > devices are not growable.
> >
> > Signed-off-by: Anthony Liguori<address@hidden>
> > ---
> > NB: this is absolutely not ideal.  A more elegant suggestion would be
> > appreciated.  I don't think NBD cleanly fits the model of a protocol as it
> > stands today.
> >
> > diff --git a/block.c b/block.c
> > index cd2ee31..a32d5dd 100644
> > --- a/block.c
> > +++ b/block.c
> > @@ -344,6 +344,12 @@ static int find_image_format(const char *filename, 
> > BlockDriver **pdrv)
> >           return ret;
> >       }
> >
> > +    if (strcmp(bs->drv->protocol_name, "nbd") == 0) {
> > +        drv = bs->drv;
> > +        bdrv_delete(bs);
> > +        goto out;
> > +    }
> >      
> Is nbd really the only protocol that behaves like this? I don't like
> hardcoding driver names in generic block layer code.
>    

I'll drop this chunk from the patch as using backing_fmt achieves the 
same goal.  The important hunk is the next one that removes assumptions 
that URIs are filenames.

Regards,

Anthony Liguori

> Kevin
>