Re: [PATCH v5 5/8] dma-buf: Make .invalidate_mapping() truly optional

["Christian König" <christian.koenig@amd.com>]

On 1/24/26 20:14, Leon Romanovsky wrote:
> From: Leon Romanovsky <leonro@nvidia.com>
> 
> The .invalidate_mapping() callback is documented as optional, yet it
> effectively became mandatory whenever importer_ops were provided. This
> led to cases where RDMA non-ODP code had to supply an empty stub.
> 
> Relax the checks in the dma-buf core so the callback can be omitted,
> allowing RDMA code to drop the unnecessary function.
> 
> Removing the stub allows the next patch to tell that RDMA does not support
> .invalidate_mapping() by checking for a NULL op.
> 
> Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
> ---
>  drivers/dma-buf/dma-buf.c             |  6 ++----
>  drivers/infiniband/core/umem_dmabuf.c | 13 -------------
>  2 files changed, 2 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> index cd68c1c0bfd7..1629312d364a 100644
> --- a/drivers/dma-buf/dma-buf.c
> +++ b/drivers/dma-buf/dma-buf.c
> @@ -947,9 +947,6 @@ dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
>  	if (WARN_ON(!dmabuf || !dev))
>  		return ERR_PTR(-EINVAL);
>  
> -	if (WARN_ON(importer_ops && !importer_ops->invalidate_mappings))
> -		return ERR_PTR(-EINVAL);
> -
>  	attach = kzalloc(sizeof(*attach), GFP_KERNEL);
>  	if (!attach)
>  		return ERR_PTR(-ENOMEM);
> @@ -1260,7 +1257,8 @@ void dma_buf_invalidate_mappings(struct dma_buf *dmabuf)
>  	dma_resv_assert_held(dmabuf->resv);
>  
>  	list_for_each_entry(attach, &dmabuf->attachments, node)
> -		if (attach->importer_ops)
> +		if (attach->importer_ops &&
> +		    attach->importer_ops->invalidate_mappings)
>  			attach->importer_ops->invalidate_mappings(attach);
>  }
>  EXPORT_SYMBOL_NS_GPL(dma_buf_invalidate_mappings, "DMA_BUF");
> diff --git a/drivers/infiniband/core/umem_dmabuf.c b/drivers/infiniband/core/umem_dmabuf.c
> index d77a739cfe7a..256e34c15e6b 100644
> --- a/drivers/infiniband/core/umem_dmabuf.c
> +++ b/drivers/infiniband/core/umem_dmabuf.c
> @@ -129,9 +129,6 @@ ib_umem_dmabuf_get_with_dma_device(struct ib_device *device,
>  	if (check_add_overflow(offset, (unsigned long)size, &end))
>  		return ret;
>  
> -	if (unlikely(!ops || !ops->invalidate_mappings))

You should probably keep "if (unlikely(!ops)).." here.

Apart from that the patch looks good to me.

Regards,
Christian.

> -		return ret;
> -
>  	dmabuf = dma_buf_get(fd);
>  	if (IS_ERR(dmabuf))
>  		return ERR_CAST(dmabuf);
> @@ -184,18 +181,8 @@ struct ib_umem_dmabuf *ib_umem_dmabuf_get(struct ib_device *device,
>  }
>  EXPORT_SYMBOL(ib_umem_dmabuf_get);
>  
> -static void
> -ib_umem_dmabuf_unsupported_move_notify(struct dma_buf_attachment *attach)
> -{
> -	struct ib_umem_dmabuf *umem_dmabuf = attach->importer_priv;
> -
> -	ibdev_warn_ratelimited(umem_dmabuf->umem.ibdev,
> -			       "Invalidate callback should not be called when memory is pinned\n");
> -}
> -
>  static struct dma_buf_attach_ops ib_umem_dmabuf_attach_pinned_ops = {
>  	.allow_peer2peer = true,
> -	.invalidate_mappings = ib_umem_dmabuf_unsupported_move_notify,
>  };
>  
>  struct ib_umem_dmabuf *
>