staging: lustre: acl: increase ACL entries limitation

Originally, the limitation of ACL entries is 32, that is not
enough for some use cases. In fact, restricting ACL entries
count is mainly for preparing the RPC reply buffer to receive
the ACL data. So we cannot make the ACL entries count to be
unlimited. But we can enlarge the RPC reply buffer to hold
more ACL entries. On the other hand, MDT backend filesystem
has its own EA size limitation. For example, for ldiskfs case,
if large EA enable, then the max ACL size is 1048492 bytes;
otherwise, it is 4012 bytes. For ZFS backend, such value is
32768 bytes. With such hard limitation, we can calculate how
many ACL entries we can have at most. This patch increases
the RPC reply buffer to match such hard limitation. For old
client, to avoid buffer overflow because of large ACL data
(more than 32 ACL entries), the MDT will forbid the old client
to access the file with large ACL data. As for how to know
whether it is old client or new, a new connection flag
OBD_CONNECT_LARGE_ACL is used for that.

Signed-off-by: Fan Yong <fan.yong@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-7473
Reviewed-on: https://review.whamcloud.com/19790


Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Li Xi <lixi@ddn.com>
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>