[Bug 1807073] Re: qemu-guest-agent stop work when fsfreeze

[Rene]

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.

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https://bugs.launchpad.net/bugs/1807073

Title:
  qemu-guest-agent stop work when fsfreeze

Status in QEMU:
  New

Bug description:
  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

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