Hello Greg,
I'd like to request the following commits (in that order) be merged into
4.4/4.9 stable branches:
b7f8a09f8097 ("btrfs: Don't clear SGID when inheriting ACLs") - this one
landed in 4.13 and was tagged for stable but it seems it got missed.
d7d824966530 ("btrfs: preserve i_mode if __btrfs_set_acl() fails") -
this one depends on the first commit for context but otherwise, should
be trivial to backport.