RDMA/mlx5: Do not allow rereg of a ODP MR

This code is completely broken, the umem of a ODP MR simply cannot be
discarded without a lot more locking, nor can an ODP mkey be blithely
destroyed via destroy_mkey().

Fixes: 6aec21f ("IB/mlx5: Page faults handling infrastructure")
Link: https://lore.kernel.org/r/20191001153821.23621-2-jgg@ziepe.ca
Reviewed-by: Artemy Kovalyov <artemyko@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/hw/mlx5/mr.c

@@ -1441,6 +1441,9 @@ int mlx5_ib_rereg_user_mr(struct ib_mr *ib_mr, int flags, u64 start,
 	if (!mr->umem)
 		return -EINVAL;
 
+	if (is_odp_mr(mr))
+		return -EOPNOTSUPP;
+
 	if (flags & IB_MR_REREG_TRANS) {
 		addr = virt_addr;
 		len = length;
@@ -1486,8 +1489,6 @@ int mlx5_ib_rereg_user_mr(struct ib_mr *ib_mr, int flags, u64 start,
 		}
 
 		mr->allocated_from_cache = 0;
-		if (IS_ENABLED(CONFIG_INFINIBAND_ON_DEMAND_PAGING))
-			mr->live = 1;
 	} else {
 		/*
 		 * Send a UMR WQE
@@ -1516,7 +1517,6 @@ int mlx5_ib_rereg_user_mr(struct ib_mr *ib_mr, int flags, u64 start,
 
 	set_mr_fields(dev, mr, npages, len, access_flags);
 
-	update_odp_mr(mr);
 	return 0;
 
 err: