Re: [PATCH v14 4/4] RDMA/mlx5: Support dma-buf based userspace memory region

[Leon Romanovsky <leon@kernel.org>]

On Tue, Dec 08, 2020 at 02:39:15PM -0800, Jianxin Xiong wrote:
> Implement the new driver method 'reg_user_mr_dmabuf'.  Utilize the core
> functions to import dma-buf based memory region and update the mappings.
>
> Add code to handle dma-buf related page fault.
>
> Signed-off-by: Jianxin Xiong <jianxin.xiong@intel.com>
> Reviewed-by: Sean Hefty <sean.hefty@intel.com>
> Acked-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
> Acked-by: Christian Koenig <christian.koenig@amd.com>
> Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> ---
>  drivers/infiniband/hw/mlx5/main.c    |   2 +
>  drivers/infiniband/hw/mlx5/mlx5_ib.h |  18 +++++
>  drivers/infiniband/hw/mlx5/mr.c      | 128 +++++++++++++++++++++++++++++++++--
>  drivers/infiniband/hw/mlx5/odp.c     |  86 +++++++++++++++++++++--
>  4 files changed, 225 insertions(+), 9 deletions(-)

<...>

>
> +
> +	umem = ib_umem_dmabuf_get(&dev->ib_dev, offset, length, fd, access_flags,
> +				  &mlx5_ib_dmabuf_attach_ops);
> +	if (IS_ERR(umem)) {
> +		mlx5_ib_dbg(dev, "umem get failed (%ld)\n", PTR_ERR(umem));
> +		return ERR_PTR(PTR_ERR(umem));

return ERR_CAST(umem);

> +	}

<...>

> +	dma_resv_lock(umem_dmabuf->attach->dmabuf->resv, NULL);
> +	err = ib_umem_dmabuf_map_pages(umem_dmabuf);
> +	if (!err) {
> +		page_size = mlx5_umem_find_best_pgsz(&umem_dmabuf->umem, mkc,
> +						     log_page_size, 0,
> +						     umem_dmabuf->umem.iova);
> +		if (unlikely(page_size < PAGE_SIZE)) {
> +			ib_umem_dmabuf_unmap_pages(umem_dmabuf);
> +			err = -EINVAL;
> +		} else {
> +			err = mlx5_ib_update_mr_pas(mr, xlt_flags);
> +		}
> +	}
> +	dma_resv_unlock(umem_dmabuf->attach->dmabuf->resv);

Let's write this section in kernel coding style, please

dma_resv_lock(umem_dmabuf->attach->dmabuf->resv, NULL);
err = ib_umem_dmabuf_map_pages(umem_dmabuf);
if (err) {
      dma_resv_unlock(umem_dmabuf->attach->dmabuf->resv);
      return err;
}
.....

Thanks