Re: [Qemu-devel] [PATCH] block:Fix FIXED base vpc be probed to raw format

[Xiaodong Gong <gordongong0350@gmail.com>]

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On Mon, Feb 9, 2015 at 10:54 PM, Stefan Hajnoczi <stefanha@gmail.com> wrote:

> On Sun, Feb 08, 2015 at 08:39:52PM +0800, Xiaodong Gong wrote:
> > When open the vpc snapshot based FIXED format, its backing file,
> > this FIXED vpc image, could be probed as a raw image, because that
> > the find_image_format just checkout the first sector.
> >
> > Add a re-probe for the last sector to FIXED base vpc image,when get
> > a NULL or raw driver in first sector probe.
> >
> > Signed-off-by: Xiaodong Gong <gongxiaodong1@huawei.com>
> > ---
> >  block.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++++-------
> >  1 file changed, 48 insertions(+), 7 deletions(-)
>
> This approach is likely to cause issues because it makes no distiction
> between headers and footers.  Most image formats only have a header and
> would now be misdetected if a raw image had a header in its last sector.
>
> When a vpc image has a backing file, does it make sense to set the
> bs->backing_format to "vpc"?  That way we'll try to open the backing
> file as a vpc image without probing.
>
> Stefan
>


It works, but this probing of format sounds good . Giving a argument of bs
to bdrv_probe and each of funtion of probe get it's own checking method is
better, but the foot-print of patch is longer.

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