Am 07.12.2011 12:50, schrieb Stefan Hajnoczi: > On Wed, Dec 7, 2011 at 11:45 AM, Kevin Wolf <kw...@redhat.com> wrote: >> Backing files may be smaller than the corresponding COW file. When >> reading directly from the backing file, qemu-img rebase must consider >> this and assume zero sectors after the end of backing files. >> >> Signed-off-by: Kevin Wolf <kw...@redhat.com> >> --- >> qemu-img.c | 42 +++++++++++++++++++++++++++++++++--------- >> 1 files changed, 33 insertions(+), 9 deletions(-) > > Reviewed-by: Stefan Hajnoczi <stefa...@linux.vnet.ibm.com> > > It almost feels like we want a bdrv_read() variation that does the > zeroing beyond end of image instead of duplicating this.
Almost. If we have a third user, it's probably worth it. Actually, if we make a bdrv_co_readv_backing() instead of a synchronous one, qcow2 would be the third user (and maybe VMDK could use it, too). That would require moving qemu-img into a coroutine first, which I think you wanted to do anyway? Kevin
