Re: [PATCH 06/20] RDMA/mlx5: Implement mlx5_ib_map_mr_sg_pi and mlx5_ib_alloc_mr_integrity

[Christoph Hellwig <hch@xxxxxx>]

>  int mlx5_ib_dereg_mr(struct ib_mr *ibmr, struct ib_udata *udata)
>  {
> -	dereg_mr(to_mdev(ibmr->device), to_mmr(ibmr));
> +	struct mlx5_ib_mr *mmr = to_mmr(ibmr);
> +
> +	if (ibmr->type == IB_MR_TYPE_INTEGRITY)
> +		dereg_mr(to_mdev(mmr->pi_mr->ibmr.device), mmr->pi_mr);
> +
> +	dereg_mr(to_mdev(ibmr->device), mmr);

Just curious: how could the device for the PI MR be different?  In other
words, why can't this just be:

	struct mlx5_ib_mr *mmr = to_mmr(ibmr);

	if (ibmr->type == IB_MR_TYPE_INTEGRITY)
		mmr = mmr->pi_mr;
	dereg_mr(to_mdev(ibmr->device), mmr);