device: 0.926
graphic: 0.867
semantic: 0.845
socket: 0.782
ppc: 0.766
mistranslation: 0.715
network: 0.710
register: 0.668
debug: 0.641
peripherals: 0.631
user-level: 0.567
vnc: 0.552
performance: 0.543
architecture: 0.513
arm: 0.495
boot: 0.490
virtual: 0.466
kernel: 0.465
PID: 0.456
x86: 0.443
i386: 0.428
VMM: 0.419
files: 0.417
hypervisor: 0.417
TCG: 0.345
permissions: 0.300
assembly: 0.295
KVM: 0.231
risc-v: 0.206

drive-mirror RBD thin
Description of problem:
I found that this problem was first discovered in 2014. There was a post 
[2014 bug description](https://lists.gnu.org/archive/html/qemu-devel/2014-10/msg01231.html )、
[2014 patch](https://patchwork.ozlabs.org/project/qemu-devel/patch/1433747185-16797-2-git-send-email-famz@redhat.com/)
mentioning this bug. 
The patch in the post said that this problem had been solved, but after trying and asking, I found that the problem had not been solved.
Later, I saw this problem in the [2017 bug description](https://forum.proxmox.com/threads/drive-mirror-rbd-thin.33250/#post-613502) forum and it was said that there was a patch to fix it, but it was not.
I tried the latest qemu version and found that this problem has not been solved.
Additional information:
nbd is normal, but rbd is wrong！