On Sat, Aug 29, 2020 at 02:11:23PM +0200, Pavel Machek wrote:
Hi!
[ Upstream commit a7f8b1c2ac21bf081b41264c9cfd6260dffa6246 ]
The incoming qgroup reserved space timing will move the data reservation
to ordered extent completely.
However in btrfs_punch_hole_lock_range() will call
btrfs_invalidate_page(), which will clear QGROUP_RESERVED bit for the
range.
In current stage it's OK, but if we're making ordered extents handle the
reserved space, then btrfs_punch_hole_lock_range() can clear the
QGROUP_RESERVED bit before we submit ordered extent, leading to qgroup
reserved space leakage.
So here change the timing to make reserve data space after
btrfs_punch_hole_lock_range().
The new timing is fine for either current code or the new code.
I'm not sure why this is queued for -stable. It is preparation for
future work, and that work is not queued for -stable.
So you understand why it was queued: it's preparation for a fix that is
relevant to 4.19 but didn't apply cleanly.
I can look into what happened next week, or if you'd sent me a backport
I'd be happy to take it.
--
Thanks,
Sasha
