See also https://gitlab.com/qemu-project/qemu/-/issues/520
** Bug watch added: gitlab.com/qemu-project/qemu/-/issues #520 https://gitlab.com/qemu-project/qemu/-/issues/520 -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1813045 Title: qemu-ga fsfreeze crashes the kernel Status in QEMU: Expired Bug description: We use mainly Cloudlinux, Debian and Centos. We experienced many crashes on our qemu instances based on Cloudlinux during a snapshot. The issue is not related to CloudLinux directly, but to Qemu agent, which does not freeze the file system(s) correctly. What is actually happening: When VM backup is invoked, Qemu agent freezes the file systems, so no single change will be made during the backup. But Qemu agent does not respect the loop* devices in freezing order (we have checked its sources), which leads to the next situation: 1) freeze loopback fs ---> send async reqs to loopback thread 2) freeze main fs 3) loopback thread wakes up and trying to write data to the main fs, which is still frozen, and this finally leads to the hung task and kernel crash. I believe this is the culprit: /dev/loop0 /tmp ext3 rw,nosuid,noexec,relatime,data=ordered 0 0 /dev/loop0 /var/tmp ext3 rw,nosuid,noexec,relatime,data=ordered 0 0 To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1813045/+subscriptions
