Re: [net-next v1 01/16] net: page_pool: factor out releasing DMA from releasing the page

[Ilias Apalodimas]

On Fri, 8 Dec 2023 at 02:52, Mina Almasry <almasrymina@xxxxxxxxxx> wrote:
>
> From: Jakub Kicinski <kuba@xxxxxxxxxx>
>
> Releasing the DMA mapping will be useful for other types
> of pages, so factor it out. Make sure compiler inlines it,
> to avoid any regressions.
>
> Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
> Signed-off-by: Mina Almasry <almasrymina@xxxxxxxxxx>
>
> ---
>
> This is implemented by Jakub in his RFC:
>
> https://lore.kernel.org/netdev/f8270765-a27b-6ccf-33ea-cda097168d79@xxxxxxxxxx/T/
>
> I take no credit for the idea or implementation. This is a critical
> dependency of device memory TCP and thus I'm pulling it into this series
> to make it revewable and mergable.
>
> ---
>  net/core/page_pool.c | 25 ++++++++++++++++---------
>  1 file changed, 16 insertions(+), 9 deletions(-)
>
> diff --git a/net/core/page_pool.c b/net/core/page_pool.c
> index c2e7c9a6efbe..ca1b3b65c9b5 100644
> --- a/net/core/page_pool.c
> +++ b/net/core/page_pool.c
> @@ -548,21 +548,16 @@ s32 page_pool_inflight(const struct page_pool *pool, bool strict)
>         return inflight;
>  }
>
> -/* Disconnects a page (from a page_pool).  API users can have a need
> - * to disconnect a page (from a page_pool), to allow it to be used as
> - * a regular page (that will eventually be returned to the normal
> - * page-allocator via put_page).
> - */
> -static void page_pool_return_page(struct page_pool *pool, struct page *page)
> +static __always_inline
> +void __page_pool_release_page_dma(struct page_pool *pool, struct page *page)
>  {
>         dma_addr_t dma;
> -       int count;
>
>         if (!(pool->p.flags & PP_FLAG_DMA_MAP))
>                 /* Always account for inflight pages, even if we didn't
>                  * map them
>                  */
> -               goto skip_dma_unmap;
> +               return;
>
>         dma = page_pool_get_dma_addr(page);
>
> @@ -571,7 +566,19 @@ static void page_pool_return_page(struct page_pool *pool, struct page *page)
>                              PAGE_SIZE << pool->p.order, pool->p.dma_dir,
>                              DMA_ATTR_SKIP_CPU_SYNC | DMA_ATTR_WEAK_ORDERING);
>         page_pool_set_dma_addr(page, 0);
> -skip_dma_unmap:
> +}
> +
> +/* Disconnects a page (from a page_pool).  API users can have a need
> + * to disconnect a page (from a page_pool), to allow it to be used as
> + * a regular page (that will eventually be returned to the normal
> + * page-allocator via put_page).
> + */
> +void page_pool_return_page(struct page_pool *pool, struct page *page)
> +{
> +       int count;
> +
> +       __page_pool_release_page_dma(pool, page);
> +
>         page_pool_clear_pp_info(page);
>
>         /* This may be the last page returned, releasing the pool, so
> --
> 2.43.0.472.g3155946c3a-goog
>

Reviewed-by: Ilias Apalodimas <ilias.apalodimas@xxxxxxxxxx>