Commits
Filipe Manana committed e6571499336
Btrfs: remove unused function btrfs_add_delayed_qgroup_reserve()
No longer used as of commit 5846a3c26873 ("btrfs: qgroup: Fix a race in
delayed_ref which leads to abort trans").
Signed-off-by: Filipe Manana <fdmanana@suse.com>