On 10/03/2016 18:37, Stefan Hajnoczi wrote:
I suggest giving the new NBD command a "type" argument:
0 - SCSI mapped/anchored values according to SCSI Get LBA Status
1 - Dirty/clean, useful for incremental backup and other blocking tracking cases
This way we don't impinge on SCSI semantics and the command can be
used for both traditional logical block provisioning and dirty bitmap
info.
When the NBD export is started in QEMU you can optionally associate it
with a bitmap. This bitmap is used to provide type=1 (dirty/clean)
status information.
Good idea. The precedent in NBD is to use bits 16..31 of the command
for flags, so it could go there.
Paolo