linux-kernel - Re: [PATCH net-next v4 1/5] page_pool: frag API support for 32-bit arch with 64-bit DMA

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Date:   Tue, 13 Jun 2023 15:30:28 +0200
From:   Alexander Lobakin <aleksander.lobakin@...el.com>
To:     Yunsheng Lin <linyunsheng@...wei.com>
CC:     <davem@...emloft.net>, <kuba@...nel.org>, <pabeni@...hat.com>,
        <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Alexander Duyck <alexander.duyck@...il.com>,
        "Saeed Mahameed" <saeedm@...dia.com>,
        Leon Romanovsky <leon@...nel.org>,
        "Eric Dumazet" <edumazet@...gle.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        <linux-rdma@...r.kernel.org>
Subject: Re: [PATCH net-next v4 1/5] page_pool: frag API support for 32-bit
 arch with 64-bit DMA

From: Yunsheng Lin <linyunsheng@...wei.com>
Date: Mon, 12 Jun 2023 21:02:52 +0800

> Currently page_pool_alloc_frag() is not supported in 32-bit
> arch with 64-bit DMA, which seems to be quite common, see
> [1], which means driver may need to handle it when using
> page_pool_alloc_frag() API.

[...]

> diff --git a/include/net/page_pool.h b/include/net/page_pool.h
> index 126f9e294389..5c7f7501f300 100644
> --- a/include/net/page_pool.h
> +++ b/include/net/page_pool.h
> @@ -33,6 +33,7 @@
>  #include <linux/mm.h> /* Needed by ptr_ring */
>  #include <linux/ptr_ring.h>
>  #include <linux/dma-direction.h>

This include is redundant now that you include dma-mapping.h.

> +#include <linux/dma-mapping.h>

As Jakub previously mentioned, this involves including dma-mapping.h,
which is relatively heavy, to each source file which includes skbuff.h,
i.e. almost the whole kernel :D
I addressed this in my series, which I hope will land soon after yours
(sending new revision in 24-48 hours), so you can leave it as it is. Or
otherwise you can pick my solution (or come up with your own :D).

>  
>  #define PP_FLAG_DMA_MAP		BIT(0) /* Should page_pool do the DMA
>  					* map/unmap

Thanks,
Olek