Am 28.06.2013 um 10:16 hat Peter Lieven geschrieben: > On 28.06.2013 10:06, Kevin Wolf wrote: > >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. > ups. > > > >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. > shall I leave this to the new 0 default until your patch is ready?
Yes, please leave vpc alone. I guess my patch will be queued before yours anyway. ;-) > >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. > ok I will mention that the value is changed for vmdk (and vpc) in the > commit message. Good idea for vmdk. For vpc, don't mention it, because see above. Kevin
