Re: [PATCH v3 1/4] block: Add trivial backing_fmt support to qcow, sheepdog, vmdk

Am 06.03.2020 um 23:51 hat Eric Blake geschrieben:

For qcow2 and qed, we want to encourage the use of -F always, as these formats can suffer from data corruption or security holes if backing format is probed. But for other formats, the backing format cannot be recorded. Making the user decide on a per-format basis whether to supply a backing format string is awkward, better is to just blindly accept a backing format argument even if it is ignored by the contraints of the format at hand.

Signed-off-by: Eric Blake <eblake@redhat.com>

I'm not sure if I agree with this reasoning. Accepting and silently ignoring -F could give users a false sense of security. If I specify a -F raw and QEMU later probes qcow2, that would be very surprising. Kevin