qemu-devel
[Top][All Lists]
Advanced

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[Qemu-devel] [Bug 1813045] [NEW] qemu-ga fsfreeze crashes the kernel


From: Michele Schillaci
Subject: [Qemu-devel] [Bug 1813045] [NEW] qemu-ga fsfreeze crashes the kernel
Date: Wed, 23 Jan 2019 17:07:36 -0000

Public bug reported:

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

** Affects: qemu
     Importance: Undecided
         Status: New

-- 
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:
  New

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



reply via email to

[Prev in Thread] Current Thread [Next in Thread]