Am 05.05.2020 um 10:54 hat Kevin Wolf geschrieben: > Am 04.05.2020 um 19:07 hat Alberto Garcia geschrieben: > > On Mon 04 May 2020 06:01:19 PM CEST, Eric Blake wrote: > > >> +_supported_fmt qcow2 > > >> +_supported_proto file > > > > > > Do we have to limit it to qcow2 and file? Yes, it's testing a bugfix > > > for qcow2, but are there other formats that it doesn't hurt to have > > > the extra testing? > > > > It doesn't work with any other format at the moment (meaning: reading > > the tail of the image after growing it returns the data from the backing > > file). > > > > Also, it seems that qemu-img's -F does not work with other formats > > either. > > > > > Also, I don't see anything preventing this from working with non-file > > > protocol. > > > > Right, that can be updated I guess (whoever commits this, feel free to > > do it). > > I don't know for which protocols it works. I know that qcow2 over nbd > doesn't work. > > But I think there is a more important problem with the test: It seems to > pass even with old binaries that don't have the fix. Is this only on my > system or do you get the same?
Ah, I do get the overflow in the calculation of the length for qcow2_cluster_zeroize(), but size_to_clusters() inside the function overflows back the other direction, so this ends up with nb_clusters = 0 and we don't do anything bad. We could probably trigger a bad case with data_file_raw=on, but then we don't have a backing file, so nothing sets BDRV_REQ_ZERO_WRITE. So I guess the bug isn't even really testable, but we just add the test in case something else in the same scenario breaks? Kevin
