ceph: zero the dir_entries memory when allocating it

This potentially will cause a bug in future if using an old ceph
version that sends a smaller inode struct, which can cause some members
to be skipped in handle_reply.

Signed-off-by: Xiubo Li <xiubli@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

fs/ceph/mds_client.c

@@ -2202,7 +2202,8 @@ int ceph_alloc_readdir_reply_buffer(struct ceph_mds_request *req,
 	order = get_order(size * num_entries);
 	while (order >= 0) {
 		rinfo->dir_entries = (void*)__get_free_pages(GFP_KERNEL |
-							     __GFP_NOWARN,
+							     __GFP_NOWARN |
+							     __GFP_ZERO,
 							     order);
 		if (rinfo->dir_entries)
 			break;