setfacl removes part of ACL when setting POSIX ACLs to Samba

setfacl removes part of ACL when setting POSIX ACLs to Samba

commit b1d93356427be6f050dc55c86eb019d173700af6 upstream.

setfacl over cifs mounts can remove the default ACL when setting the
(non-default part of) the ACL and vice versa (we were leaving at 0
rather than setting to -1 the count field for the unaffected
half of the ACL.  For example notice the setfacl removed
the default ACL in this sequence:

steven@steven-GA-970A-DS3:~/cifs-2.6$ getfacl /mnt/test-dir ; setfacl
-m default:user:test:rwx,user:test:rwx /mnt/test-dir
getfacl: Removing leading '/' from absolute path names
user::rwx
group::r-x
other::r-x
default:user::rwx
default:user:test:rwx
default:group::r-x
default:mask::rwx
default:other::r-x

steven@steven-GA-970A-DS3:~/cifs-2.6$ getfacl /mnt/test-dir
getfacl: Removing leading '/' from absolute path names
user::rwx
user:test:rwx
group::r-x
mask::rwx
other::r-x

Signed-off-by: Steve French <smfrench@gmail.com>
Acked-by: Jeremy Allison <jra@samba.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>