On 3/11/20 7:56 AM, Peter Krempa wrote:
On start of the commit job, we need to disable any active bitmap in the base. Use qemuBlockBitmapsHandleCommitStart to calculate which and call the appropriate QMP APIs. We use blockdev-reopen to make the 'base' writable to disable the bitmaps. Signed-off-by: Peter Krempa <pkrempa@xxxxxxxxxx> --- src/qemu/qemu_driver.c | 43 +++++++++++++++++++++++++++++++++++++++++- 1 file changed, 42 insertions(+), 1 deletion(-)
Someday, it would be nice if qemu let us do this without requiring us to do the reopen step ourselves, but in the meantime, this looks like it works. Design-wise, I'm still not convinced why we have to disable the bitmaps in the base prior to the commit (as the only thing a bitmap is good for is for cumulative merging in determining how much of an image to expose over a future differential backup, but that differential is the same whether we write bits in one or multiple bitmaps as part of the commit operation). But code wise, this looks accurate.
Reviewed-by: Eric Blake <eblake@xxxxxxxxxx> -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org
