Incorrect diskwrite accounting by pvestatd after upgrade from 6.4 to 7.0

[eider]

After upgrade from 6.4 to 7.0 all CTs report diskwrite as 0. diskread continues to be accounted for properly. VMs are not affected by this. Observed on all nodes; standard configuration with rootfs stored as raw file on ext4 filesystem.

proxmox-ve: 7.0-2 (running kernel: 5.11.22-2-pve)
pve-manager: 7.0-10 (running version: 7.0-10/d2f465d3)
pve-kernel-5.11: 7.0-5
pve-kernel-helper: 7.0-5
pve-kernel-5.11.22-2-pve: 5.11.22-3
pve-kernel-5.11.22-1-pve: 5.11.22-2
ceph-fuse: 14.2.21-1
corosync: 3.1.2-pve2
criu: 3.15-1+pve-1
glusterfs-client: 9.2-1
ifupdown2: 3.1.0-1+pmx2
ksm-control-daemon: 1.4-1
libjs-extjs: 7.0.0-1
libknet1: 1.21-pve1
libproxmox-acme-perl: 1.1.1
libproxmox-backup-qemu0: 1.2.0-1
libpve-access-control: 7.0-4
libpve-apiclient-perl: 3.2-1
libpve-common-perl: 7.0-5
libpve-guest-common-perl: 4.0-2
libpve-http-server-perl: 4.0-2
libpve-storage-perl: 7.0-9
libspice-server1: 0.14.3-2.1
lvm2: 2.03.11-2.1
lxc-pve: 4.0.9-2
lxcfs: 4.0.8-pve2
novnc-pve: 1.2.0-3
proxmox-backup-client: 2.0.4-1
proxmox-backup-file-restore: 2.0.4-1
proxmox-mini-journalreader: 1.2-1
proxmox-widget-toolkit: 3.3-4
pve-cluster: 7.0-3
pve-container: 4.0-8
pve-docs: 7.0-5
pve-edk2-firmware: 3.20200531-1
pve-firewall: 4.2-2
pve-firmware: 3.2-4
pve-ha-manager: 3.3-1
pve-i18n: 2.4-1
pve-qemu-kvm: 6.0.0-2
pve-xtermjs: 4.12.0-1
qemu-server: 7.0-10
smartmontools: 7.2-pve2
spiceterm: 3.2-2
vncterm: 1.7-1
zfsutils-linux: 2.0.5-pve1

arch: amd64
cores: 2
hostname: cardinal
memory: 2048
net0: name=eth0,bridge=vmbr0,firewall=1,hwaddr=86:F9:BD:71:7C:24,ip=dhcp,type=veth
onboot: 1
ostype: debian
rootfs: local:112/vm-112-disk-0.raw,mountoptions=noatime,size=16G
swap: 0
unprivileged: 1

dir: local-images
        path /var/lib/vz-images
        content vztmpl,iso
        shared 0

dir: local
        path /var/lib/vz
        content snippets,images,rootdir
        shared 0

dir: backup
        path /backup/pve/vzdump
        content backup
        prune-backups keep-daily=6,keep-last=3,keep-weekly=2
        shared 0

loop0               7:0    0     8G  0 loop
loop1               7:1    0    16G  0 loop
loop2               7:2    0     8G  0 loop
loop3               7:3    0     8G  0 loop
loop4               7:4    0    16G  0 loop
sda                 8:0    0 465.3G  0 disk
└─raid-backup_pve 253:3    0   250G  0 lvm
  └─backup_pve    253:5    0   250G  0 crypt /backup/pve
sdb                 8:16   0 186.3G  0 disk
├─sdb1              8:17   0  1007K  0 part
├─sdb2              8:18   0   512M  0 part  /boot/efi
└─sdb3              8:19   0 185.8G  0 part
  ├─pve-root      253:0    0  27.8G  0 lvm   /
  ├─pve-data      253:1    0 156.1G  0 lvm
  │ └─data        253:4    0   156G  0 crypt /var/lib/vz
  └─pve-swap      253:2    0     2G  0 lvm   [SWAP]

Previously reported at:
- https://forum.proxmox.com/threads/proxmox-ve-7-0-released.92007/page-4#post-401347
- https://forum.proxmox.com/threads/p...ata-in-metrics-after-migration-to-pve7.92503/
- https://forum.proxmox.com/threads/proxmox-ve-7-0-released.92007/page-6#post-402231