ctime not consistently updated for xattr updates

[riconnon]

When I create a file then add 2 ACLs to it using setfacl I get inconsistent updates of the ctime attribute.
I did the following:

zfs create tank/fs
zfs set xattr=sa tank
zfs set acltype=posixacl tank
touch /tank/fs/testfile
stat /tank/fs/testfile
setfacl -m u:user0:rwx /tank/fs/testfile
stat /tank/fs/testfile
setfacl -m u:user1:rwx /tank/fs/testfile
stat /tank/fs/testfile

I see the ctime changes between the first two stat outputs but not in the third.

[riconnon]

The same behaviour happens without xattr=sa too.

[riconnon]

Looking at this with relatively little prior knowledge it seems to me that zpl_xattr_set should probably always update ctime.