ceph: add get_name() NFS export callback

Use the newly introduced LOOKUPNAME MDS request to connect child
inode to its parent directory.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Reviewed-by: Sage Weil <sage@inktank.com>
diff --git a/include/linux/ceph/ceph_fs.h b/include/linux/ceph/ceph_fs.h
index 25bfb0e..35f345f 100644
--- a/include/linux/ceph/ceph_fs.h
+++ b/include/linux/ceph/ceph_fs.h
@@ -332,6 +332,7 @@
 	CEPH_MDS_OP_LOOKUPHASH = 0x00102,
 	CEPH_MDS_OP_LOOKUPPARENT = 0x00103,
 	CEPH_MDS_OP_LOOKUPINO  = 0x00104,
+	CEPH_MDS_OP_LOOKUPNAME = 0x00105,
 
 	CEPH_MDS_OP_SETXATTR   = 0x01105,
 	CEPH_MDS_OP_RMXATTR    = 0x01106,