[Samba] Why did samba4 remove "force security mode" and "force directory security"?

[Sense Zeng]

I just upgrade samba 3.6 to samba 4.3, folow the ubuntu 12.04 upgrade to
14.04. And I found out Samba 4 removed "force security mode" and "force
directory security" from smb.conf. I don't understand why remove them,
because I think they are irreplaceable.
I need to keep some permission of the file or directory in the samba share
and make sure them can't change by anyone even the file ownner. With "force
security mode" and "force directory security" I can easy to do it. But in
Samba 4 I can't use the same setting any more, and I can't find the instead
setting in smb.conf.
Could anyone tell me why "force security mode" and "force directory
security" have been remove for Samba 4?