Sent the v2 version of this patch integrated in v9 verison of VHD_DEFFERING patch. Fixed this problem with backing_format.
On Sat, Feb 14, 2015 at 10:13 AM, Xiaodong Gong <gordongong0...@gmail.com> wrote: > > > On Wed, Feb 11, 2015 at 9:39 PM, Stefan Hajnoczi <stefa...@redhat.com> > wrote: > >> On Tue, Feb 10, 2015 at 11:04:31PM +0800, Xiaodong Gong wrote: >> > On Mon, Feb 9, 2015 at 10:54 PM, Stefan Hajnoczi <stefa...@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 <gongxiaodo...@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. >> >> I'm not suggesting a longer patch. >> >> Can the vpc .bdrv_open() code that loads the backing filename also set >> bs->backing_format to "vpc" so QEMU will always use vpc for the backing >> file? >> >> Stefan >> > > It is not a perfect choice, but a right one. I will give a v2 of patch. >
