** Description changed:
+ == SRU Justification, EOAN ==
+
+ ZFS can deadlock, this can be sometimes triggered with a zfs rollback -
+ "the zfs_resume_fs() code path may cause zfs to spawn new threads as it
+ reinstantiates the suspended fs's zil. When a new thread is spawned, the
+ kernel may attempt to free memory for that thread by freeing some
+ unreferenced inodes. If it happens to select inodes that are a a part of
+ the suspended fs a deadlock will occur because freeing inodes requires
+ holding the fs's z_teardown_inactive_lock which is still held from the
+ suspend."
+
+ == The Fix ==
+
+ Backport of ZFS upstream commit e7a2fa70c3b0d8c8cee2b484038bb5623c7c1ea9
+ ("Fix deadlock in 'zfs rollback'")
+
+ The backport is relatively simple context wiggle.
+
+ == Test Case ==
+
+ This is hard to trigger so testing is non-trivial. To check for
+ regressions we run the entire Ubuntu ZFS regression test suite. Without
+ the fix rollbacks can very occasionally trip this issue. With the test,
+ it's not possible.
+
+ == Regression Potential ==
+
+ The fix adds in an extra z_suspended flag to track suspended state and
+ adds an extra reference to stop the kernel from free'ing inodes on a
+ suspected file system. The changes are small and are well-used in
+ upstream ZFS so I believe if a regression was to have occurred it would
+ have been found by the regression testing.
+
+ --------------------- Original Bug Report Below -------------------
+
Hopefully this is the correct bug tracker to report this on.
Recently, I ran into a bug in ZFS as shipped in Ubuntu 19.10 that caused
the kernel to deadlock and the system to eventually hang.
I was advised by a ZFS on Linux project maintainer that this was a bug
that was fixed in 0.8.2.
The relevant pull request is here:
https://github.com/zfsonlinux/zfs/pull/9203
It would probably be a good idea to backport that pull request into
19.10's build of ZFS.
--
You received this bug notification because you are a member of Ubuntu
Bugs, which is subscribed to Ubuntu.
https://bugs.launchpad.net/bugs/1847832
Title:
Backport ZoL pull request 9203 into the official packages.
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/zfs-linux/+bug/1847832/+subscriptions
--
ubuntu-bugs mailing list
[email protected]
https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
