Am 27.06.2013 um 15:52 hat Peter Lieven geschrieben: > .has_zero_init defaults to 1 for all formats and protocols. > > this is a dangerous default since this means that all > new added drivers need to manually overwrite it to 0 if > they do not ensure that a device is zero initialized > after bdrv_create(). > > if a driver needs to explicitly set this value to > 1 its easier to verify the correctness in the review process. > > during review of the existing drivers it turned out > that ssh and gluster had a wrong default of 1. > both protocols support host_devices as backend > which are not by default zero initialized. this > wrong assumption will lead to possible corruption > if qemu-img convert is used to write to such a backend. > > a similar problem with the wrong default existed for > iscsi mose likely because the driver developer did > oversee the default value of 1. > > Signed-off-by: Peter Lieven <p...@kamp.de> > --- > block.c | 8 +++++++- > block/qcow.c | 1 + > block/qcow2.c | 1 + > block/qed.c | 1 + > block/raw-posix.c | 10 +--------- > block/raw-win32.c | 7 +------ > block/rbd.c | 1 + > block/sheepdog.c | 1 + > block/vdi.c | 1 + > block/vmdk.c | 1 + > include/block/block.h | 1 + > 11 files changed, 17 insertions(+), 16 deletions(-)
You forgot cow, which is also a simple case that can be handled in this patch. vpc is still easy, but a bit more complicated than a constant return 1, because it depends on the subformat whether a new image will inherit the has_zero_init property from the underlying storage or whether it always produces zeros (for VHD_FIXED type images, it's basically raw + footer). I'll send a separate patch for this. A similar situation exists for vmdk, I think, just that the difference can be per extent there. I guess we need to return 0 if one of the extents is flat and has an underlying storage returning 0. I'll leave this part to Fam. For now, please remove the bdrv_has_zero_init_1 for vmdk from this patch as it's unsafe. Kevin
