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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Message-ID: <6db097ba-c3fe-6e45-3c39-c21b4d9e16ef@huawei.com>
Date:   Wed, 14 Jun 2023 11:36:28 +0800
From:   Yunsheng Lin <linyunsheng@...wei.com>
To:     Alexander Lobakin <aleksander.lobakin@...el.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

On 2023/6/13 21:30, Alexander Lobakin wrote:
> 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 am not sure I understand the part about 'includes skbuff.h' yet, it seems
'skbuff.h' does not have anything related to this patch?

> 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).

Do you mean by removing "#include <linux/dma-direction.h>" as dma-mapping.h
has included dma-direction.h?
But I am not sure if there is any hard rule about not explicitly including
a .h which is implicitly included. What if the dma-mapping.h is changed to not
include dma-direction.h anymore?

Anyway, it seems it is unlikely to not include dma-direction.h in dma-mapping.h,
Will remove the "#include <linux/dma-direction.h>" if there is another version
needed for this patchset:)

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