Hi, the following patches try to fix a long outstanding issue with qgroups
and snapshot deletion. The core problem is that btrfs_drop_snapshot will
skip shared extents during it's tree walk. This results in an inconsistent
qgroup state once the drop is processed.
The first patch adds some tracing which I found very useful in debugging
qgroup operations. The second patch is an actual fix to the problem.
Even with this patch series, we still have some inconsistency in qgroups
when a snapshot is deleted. As far as I can tell this is because shared
subtree roots are not completely skipped and may get passed to the qgroup
subsystem via a number of ref operations that happen during drop snapshot.
I am working on a fix for that issue, but feel that what I have here gets us
90% of the way to a full fix.
Please review, thanks. Diffstat follows,
--Mark
fs/btrfs/extent-tree.c | 234 +++++++++++++++++++++++++++++++++++++++++++
fs/btrfs/qgroup.c | 169 +++++++++++++++++++++++++++++--
fs/btrfs/qgroup.h | 1
fs/btrfs/super.c | 1
include/trace/events/btrfs.h | 57 ++++++++++
5 files changed, 456 insertions(+), 6 deletions(-)
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