This is a less hacky version of my first attempt:
https://lists.gnu.org/archive/html/qemu-devel/2018-06/msg05993.html

The worst part of the hack (taking a semicolon-separated list of
requests to hand the server) is completely dropped, the member
field is renamed to reflect what it is doing, and I've added an
iotests to help us in regression testing.

I'd REALLY like to send a pull request before soft freeze (tomorrow
morning is approaching fast!) that includes these patches, so that
qemu 3.0 at least has experimental access to all the pieces needed
for playing with incremental backups.

Eric Blake (2):
  nbd/client: Add x-dirty-bitmap to query bitmap from server
  iotests: New test 223 for exporting dirty bitmap over NBD

 qapi/block-core.json       |   7 ++-
 block/nbd-client.h         |   1 +
 include/block/nbd.h        |   1 +
 block/nbd-client.c         |   3 +
 block/nbd.c                |  10 +++-
 nbd/client.c               |   4 +-
 tests/qemu-iotests/223     | 138 +++++++++++++++++++++++++++++++++++++++++++++
 tests/qemu-iotests/223.out |  49 ++++++++++++++++
 tests/qemu-iotests/group   |   1 +
 9 files changed, 209 insertions(+), 5 deletions(-)
 create mode 100755 tests/qemu-iotests/223
 create mode 100644 tests/qemu-iotests/223.out

-- 
2.14.4

On 07/02/2018 02:14 PM, Eric Blake wrote:
> This is a less hacky version of my first attempt:
> https://lists.gnu.org/archive/html/qemu-devel/2018-06/msg05993.html
> 
> The worst part of the hack (taking a semicolon-separated list of
> requests to hand the server) is completely dropped, the member
> field is renamed to reflect what it is doing, and I've added an
> iotests to help us in regression testing.
> 
> I'd REALLY like to send a pull request before soft freeze (tomorrow
> morning is approaching fast!) that includes these patches, so that
> qemu 3.0 at least has experimental access to all the pieces needed
> for playing with incremental backups.
> 
> Eric Blake (2):
>    nbd/client: Add x-dirty-bitmap to query bitmap from server
>    iotests: New test 223 for exporting dirty bitmap over NBD

For patchew (maybe? does patchew run iotests?)

Based-on: 
https://lists.gnu.org/archive/html/qemu-devel/2018-06/msg06747.html
nbd/server: Fix dirty bitmap logic regression

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org