LU-4222 mdt: extra checking for getattr RPC.

Check whether getattr RPC can hold layout MD(RMF_MDT_MD),
in case the client sends some invalid RPC, which can
cause panic on MDT.

Client will retrieve cl_max_md_size/cl_default_md_size
from MDS during mount process, so it will initialize
cl_max_md_size/cl_default_md_size before sending getattr
to MDS.

Signed-off-by: wang di <di.wang@intel.com>
Change-Id: I43bbe54c37360242bb7a3cd2aa8d90c2b9e0baf1
Reviewed-on: http://review.whamcloud.com/8599
Reviewed-by: Fan Yong <fan.yong@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
LU-3531 llite: move dir cache to MDC layer

Move directory entries cache from llite to MDC, so client
side dir stripe will use independent hash function(in LMV),
which does not need to be tightly coupled with the backend
storage dir-entry hash function. With striped directory, it
will be 2-tier hash, LMV calculate hash value according to the
name and hash-type in layout, then each MDT will store these
entry in disk by its own hash.

Signed-off-by: wang di <di.wang@intel.com>
Change-Id: I14bb6bd81aad6fd59dcc22cf4bcea9d341dca2a1
Reviewed-on: http://review.whamcloud.com/7043
Tested-by: Jenkins
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>