ceph: initial CEPH_FEATURE_FS_FILE_LAYOUT_V2 support

Add support for the format change of MClientReply/MclientCaps.
Also add code that denies access to inodes with pool_ns layouts.

Signed-off-by: Yan, Zheng <zyan@redhat.com>
Reviewed-by: Sage Weil <sage@redhat.com>
diff --git a/include/linux/ceph/ceph_features.h b/include/linux/ceph/ceph_features.h
index c1ef6f1..15151f3 100644
--- a/include/linux/ceph/ceph_features.h
+++ b/include/linux/ceph/ceph_features.h
@@ -75,6 +75,7 @@
 #define CEPH_FEATURE_CRUSH_TUNABLES5	(1ULL<<58) /* chooseleaf stable mode */
 // duplicated since it was introduced at the same time as CEPH_FEATURE_CRUSH_TUNABLES5
 #define CEPH_FEATURE_NEW_OSDOPREPLY_ENCODING   (1ULL<<58) /* New, v7 encoding */
+#define CEPH_FEATURE_FS_FILE_LAYOUT_V2       (1ULL<<58) /* file_layout_t */
 
 /*
  * The introduction of CEPH_FEATURE_OSD_SNAPMAPPER caused the feature