Re: [PATCH v4 3/6] io_uring/zcrx: introduce io_populate_area_dma

[David Wei <dw@davidwei.uk>]

On 2025-07-02 07:29, Pavel Begunkov wrote:
> Add a helper that initialises page-pool dma addresses from a sg table.
> It'll be reused in following patches.
> 
> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
> ---
>   io_uring/zcrx.c | 56 +++++++++++++++++++++++++++----------------------
>   1 file changed, 31 insertions(+), 25 deletions(-)
> 
> diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c
> index 2cde88988260..cef0763010a0 100644
> --- a/io_uring/zcrx.c
> +++ b/io_uring/zcrx.c
> @@ -47,6 +47,35 @@ static inline struct page *io_zcrx_iov_page(const struct net_iov *niov)
>   	return area->mem.pages[net_iov_idx(niov)];
>   }
>   
> +static int io_populate_area_dma(struct io_zcrx_ifq *ifq,
> +				struct io_zcrx_area *area,
> +				struct sg_table *sgt, unsigned long off)
> +{
> +	struct scatterlist *sg;
> +	unsigned i, niov_idx = 0;
> +
> +	for_each_sgtable_dma_sg(sgt, sg, i) {
> +		dma_addr_t dma = sg_dma_address(sg);
> +		unsigned long sg_len = sg_dma_len(sg);
> +		unsigned long sg_off = min(sg_len, off);
> +
> +		off -= sg_off;
> +		sg_len -= sg_off;
> +		dma += sg_off;
> +
> +		while (sg_len && niov_idx < area->nia.num_niovs) {
> +			struct net_iov *niov = &area->nia.niovs[niov_idx];
> +
> +			if (net_mp_niov_set_dma_addr(niov, dma))
> +				return -EFAULT;
> +			sg_len -= PAGE_SIZE;
> +			dma += PAGE_SIZE;
> +			niov_idx++;
> +		}
> +	}
> +	return 0;
> +}
> +
>   static void io_release_dmabuf(struct io_zcrx_mem *mem)
>   {
>   	if (!IS_ENABLED(CONFIG_DMA_SHARED_BUFFER))
> @@ -119,33 +148,10 @@ static int io_import_dmabuf(struct io_zcrx_ifq *ifq,
>   
>   static int io_zcrx_map_area_dmabuf(struct io_zcrx_ifq *ifq, struct io_zcrx_area *area)
>   {
> -	unsigned long off = area->mem.dmabuf_offset;
> -	struct scatterlist *sg;
> -	unsigned i, niov_idx = 0;
> -
>   	if (!IS_ENABLED(CONFIG_DMA_SHARED_BUFFER))
>   		return -EINVAL;
> -
> -	for_each_sgtable_dma_sg(area->mem.sgt, sg, i) {
> -		dma_addr_t dma = sg_dma_address(sg);
> -		unsigned long sg_len = sg_dma_len(sg);
> -		unsigned long sg_off = min(sg_len, off);
> -
> -		off -= sg_off;
> -		sg_len -= sg_off;
> -		dma += sg_off;
> -
> -		while (sg_len && niov_idx < area->nia.num_niovs) {
> -			struct net_iov *niov = &area->nia.niovs[niov_idx];
> -
> -			if (net_mp_niov_set_dma_addr(niov, dma))
> -				return -EFAULT;
> -			sg_len -= PAGE_SIZE;
> -			dma += PAGE_SIZE;
> -			niov_idx++;
> -		}
> -	}
> -	return 0;
> +	return io_populate_area_dma(ifq, area, area->mem.sgt,
> +				    area->mem.dmabuf_offset);
>   }
>   
>   static int io_import_umem(struct io_zcrx_ifq *ifq,

Reviewed-by: David Wei <dw@davidwei.uk>