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author | Filipe Manana <fdmanana@suse.com> | 2023-06-19 19:21:50 +0300 |
---|---|---|
committer | David Sterba <dsterba@suse.com> | 2023-06-19 21:29:25 +0300 |
commit | 8a4a0b2a3eaf75ca8854f856ef29690c12b2f531 (patch) | |
tree | 6c77ed5162acca0343b1d70f8bcb99bd39d003a8 /fs/jffs2 | |
parent | 08eb2ad9db0a1f65786ab9133d6fe1683c0647c8 (diff) | |
download | linux-8a4a0b2a3eaf75ca8854f856ef29690c12b2f531.tar.xz |
btrfs: fix race between quota disable and relocation
If we disable quotas while we have a relocation of a metadata block group
that has extents belonging to the quota root, we can cause the relocation
to fail with -ENOENT. This is because relocation builds backref nodes for
extents of the quota root and later needs to walk the backrefs and access
the quota root - however if in between a task disables quotas, it results
in deleting the quota root from the root tree (with btrfs_del_root(),
called from btrfs_quota_disable().
This can be sporadically triggered by test case btrfs/255 from fstests:
$ ./check btrfs/255
FSTYP -- btrfs
PLATFORM -- Linux/x86_64 debian0 6.4.0-rc6-btrfs-next-134+ #1 SMP PREEMPT_DYNAMIC Thu Jun 15 11:59:28 WEST 2023
MKFS_OPTIONS -- /dev/sdc
MOUNT_OPTIONS -- /dev/sdc /home/fdmanana/btrfs-tests/scratch_1
btrfs/255 6s ... _check_dmesg: something found in dmesg (see /home/fdmanana/git/hub/xfstests/results//btrfs/255.dmesg)
- output mismatch (see /home/fdmanana/git/hub/xfstests/results//btrfs/255.out.bad)
--- tests/btrfs/255.out 2023-03-02 21:47:53.876609426 +0000
+++ /home/fdmanana/git/hub/xfstests/results//btrfs/255.out.bad 2023-06-16 10:20:39.267563212 +0100
@@ -1,2 +1,4 @@
QA output created by 255
+ERROR: error during balancing '/home/fdmanana/btrfs-tests/scratch_1': No such file or directory
+There may be more info in syslog - try dmesg | tail
Silence is golden
...
(Run 'diff -u /home/fdmanana/git/hub/xfstests/tests/btrfs/255.out /home/fdmanana/git/hub/xfstests/results//btrfs/255.out.bad' to see the entire diff)
Ran: btrfs/255
Failures: btrfs/255
Failed 1 of 1 tests
To fix this make the quota disable operation take the cleaner mutex, as
relocation of a block group also takes this mutex. This is also what we
do when deleting a subvolume/snapshot, we take the cleaner mutex in the
cleaner kthread (at cleaner_kthread()) and then we call btrfs_del_root()
at btrfs_drop_snapshot() while under the protection of the cleaner mutex.
Fixes: bed92eae26cc ("Btrfs: qgroup implementation and prototypes")
CC: stable@vger.kernel.org # 5.4+
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs/jffs2')
0 files changed, 0 insertions, 0 deletions