** Changed in: linux (Ubuntu)
Importance: Undecided => High
** Also affects: linux (Ubuntu Bionic)
Importance: High
Status: Confirmed
** Tags added: bionic kernel-da-key
--
You received this bug notification because you are a member of Kernel
Packages, which is subscribed to linux in Ubuntu.
https://bugs.launchpad.net/bugs/1765998
Title:
FS access deadlock with btrfs quotas enabled
Status in linux package in Ubuntu:
Confirmed
Status in linux source package in Bionic:
Confirmed
Bug description:
I'm running into an issue on Ubuntu Bionic (but not Xenial) where
shortly after boot, under heavy load from many LXD containers starting
at once, access to the btrfs filesystem that the containers are on
deadlocks.
The issue is quite hard to reproduce on other systems, quite likely
related to the size of the filesystem involved (4 devices with a total
of 8TB, millions of files, ~20 subvolumes with tens of snapshots each)
and the access pattern from many LXD containers at once. It definitely
goes away when disabling btrfs quotas though. Another prerequisite to
trigger this bug may be the container subvolumes sharing extents (from
their parent image or due to deduplication).
I can only reliably reproduce it on a production system that I can only do
very limited testing on, however I have been able to gather the following
information:
- Many threads are stuck, trying to aquire locks on various tree roots, which
are never released by their current holders.
- There always seem to be (at least) two threads executing rmdir syscalls
which are creating the circular dependency: One of them is in btrfs_cow_block
=> ... => btrfs_qgroup_trace_extent_post => ... => find_parent_nodes and wants
to acquire a lock that was already aquired by btrfs_search_slot of the other
rmdir.
- Reverting this patch seems to prevent it from happening:
https://patchwork.kernel.org/patch/9573267/
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1765998/+subscriptions
--
Mailing list: https://launchpad.net/~kernel-packages
Post to : kernel-packages@lists.launchpad.net
Unsubscribe : https://launchpad.net/~kernel-packages
More help : https://help.launchpad.net/ListHelp
