From: Launchpad Bug Tracker <1813045@bugs.launchpad.net>
To: qemu-devel@nongnu.org
Subject: [Bug 1813045] Re: qemu-ga fsfreeze crashes the kernel
Date: Sun, 20 Jun 2021 04:17:23 -0000 [thread overview]
Message-ID: <162416264382.7948.13350592574705390223.malone@loganberry.canonical.com> (raw)
In-Reply-To: 154826325670.29740.8985180444326228276.malonedeb@soybean.canonical.com
[Expired for QEMU because there has been no activity for 60 days.]
** Changed in: qemu
Status: Incomplete => Expired
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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
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next prev parent reply other threads:[~2021-06-20 4:29 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-23 17:07 [Qemu-devel] [Bug 1813045] [NEW] qemu-ga fsfreeze crashes the kernel Michele Schillaci
2021-04-20 8:04 ` [Bug 1813045] " Thomas Huth
2021-06-20 4:17 ` Launchpad Bug Tracker [this message]
2021-08-09 9:43 ` Thomas Huth
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