ceph: support getting ceph.dir.pin vxattr

Link: http://tracker.ceph.com/issues/37576
Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index e87544e..ddfb6a4 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -157,6 +157,13 @@
 			ceph_decode_64_safe(p, end, change_attr, bad);
 		}
 
+		/* dir pin */
+		if (struct_v >= 2) {
+			ceph_decode_32_safe(p, end, info->dir_pin, bad);
+		} else {
+			info->dir_pin = -ENODATA;
+		}
+
 		*p = end;
 	} else {
 		if (features & CEPH_FEATURE_MDS_INLINE_DATA) {
@@ -187,6 +194,8 @@
 				*p += info->pool_ns_len;
 			}
 		}
+
+		info->dir_pin = -ENODATA;
 	}
 	return 0;
 bad: