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

[Kevin Wolf]

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 at 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