On 12/7/18 5:21 AM, Vladimir Sementsov-Ogievskiy wrote:
01.12.2018 1:03, Eric Blake wrote:
Commit 3d068aff forgot to advertise available qemu: contexts
when the client requests a list with 0 queries. Furthermore,
3.0 shipped with a qemu-img hack of x-dirty-bitmap (commit
216ee365) that _silently_ acts as though the entire image is
clean if a requested bitmap is not present. Both bugs have
been recently fixed to give full output from the start, and
to refuse a connection if a requested x-dirty-bitmap was not
found.
Still, it is likely that there will be users that have to
work with a mix of old and new qemu versions, depending on
which features get backported where, at which point being
able to rely on 'qemu-img --list' output to know for sure
whether a given NBD export has the desired dirty bitmap is
much nicer than blindly connecting and risking that the
entire image may appear clean. We can make our --list code
smart enough to work around buggy servers by tracking
whether we've seen any qemu: replies in the original 0-query
list; if not, recurse to a single query on "qemu:" (which
may still have no replies, but then we know for sure we
didn't trip up on the server bug).
related thing:
should we document these bugs with corresponding version numbers in
docs/interop/nbd.txt?
Might be useful. I'll add that as another patch in my v2 series.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
