qemu-guest-agent stop work when fsfreeze

[Hongquan Zhu]

Create a live snapshot, we should first to fsfreeze the file system. We do have only one disk mounted to /:
Filesystem Size Used Avail Use% Mounted on
udev 48G 0 48G 0% /dev
tmpfs 9.5G 8.7M 9.5G 1% /run
/dev/vda1 485G 1.5G 484G 1% /
tmpfs 48G 0 48G 0% /dev/shm
tmpfs 5.0M 0 5.0M 0% /run/lock
tmpfs 48G 0 48G 0% /sys/fs/cgroup
tmpfs 9.5G 0 9.5G 0% /run/user/0

snapshot action is OK, when we restore the snapshot, the file system became read-only, and syslog seems stop writing until we fsck /dev/vda1 and mount -o rw,remount /:
Dec 5 00:39:16 systemd[1]: Started Session 180 of user root.
Dec 5 00:45:05 qemu-ga: info: guest-fsfreeze called
Dec 5 07:00:45 kernel: [ 114.623823] EXT4-fs (vda1): re-mounted. Opts: (null)

So after snapshoting, wo do fsthaw the file system, maybe the qga dose not respond or stop work, this action dose not execute successfully and there is no log to show the status of qemu-guest-agent.

Version:
libvirt 1.2.17
qemu 2.3.0
qemu-guest-agent 2.5

[sles (slesru)]

Just got almost the same
Ubuntu 16.04 as guest on Centos 7 host,
all will latest updates.

Execute of
virsh qemu-agent-command inetgw2 '{"execute":"guest-fsfreeze-freeze"}'

failed with agent not available ( or something like this), but fsfreeze executed in OS
Apr 7 02:28:54 inetgw2 qemu-ga: info: guest-fsfreeze called

snapshot was created
after this
virsh qemu-agent-command inetgw2 '{"execute":"guest-fsfreeze-thaw"}'
failed too with agent not available

So Ubuntu 16.04 VM stuck in freezed i/o state.
 qemu-guest-age 1:2.5+dfsg-5

Same version...

Thank you!

[sles (slesru)]

btw,I run OEL7 VM on the same host and Ubuntu 18.04 VM,
both have newer qemu-guest-agent:

18.04: qemu-guest-age 1:2.11+dfsg-

OEL7: rpm -qi qemu-guest-agent
Name : qemu-guest-agent
Epoch : 10
Version : 2.12.0
Release : 2.el7

Never had this problem on both oh these.

[Hongquan Zhu (zhuhq)]

But it happens in some times， this problem dose not occur 100 percent。I can not reproduce when I want to find WHY。So it‘s dangerous in my production environment。

[Rene (dokbua)]

I have a problem with fsfreeze that looks very similar to this, though I'm of course not 100% sure it's the same.

When I try to snapshot one server, fsfreeze-freeze hangs, and after having timeout'ed the qemu agent has crashed:

# qm guest cmd 105 fsfreeze-status
thawed
# qm guest cmd 105 fsfreeze-freeze
^C << hangs, having to break out of the command
# qm guest cmd 105 fsfreeze-status
QEMU guest agent is not running
# qm reset 105 --skiplock
# qm guest cmd 105 fsfreeze-status
thawed

Host is Proxmox 5, VM is Centos 7 with Cpanel. This happens every time I try to snapshot the server. Other VM's on the host freeze fine without problem.

I don't find anything interesting under /var/log. Please let me know if there is anything I can do to help debug this problem.

[Thomas Huth (th-huth)]

The QEMU project is currently considering to move its bug tracking to another system. For this we need to know which bugs are still valid and which could be closed already. Thus we are setting older bugs to "Incomplete" now.
If you still think this bug report here is valid, then please switch the state back to "New" within the next 60 days, otherwise this report will be marked as "Expired". Or mark it as "Fix Released" if the problem has been solved with a newer version of QEMU already. Thank you and sorry for the inconvenience.

[Launchpad Janitor (janitor)]

[Expired for QEMU because there has been no activity for 60 days.]

[Thomas Huth (th-huth)]

Re-opened in the new bug tracker here: https://gitlab.com/qemu-project/qemu/-/issues/520