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Date: Sat, 16 Dec 2023 18:45:15 -0700
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Subject: Re: [RFC PATCH net-next v1 2/4] net: introduce abstraction for
 network memory
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To: Mina Almasry <almasrymina@google.com>, Jakub Kicinski <kuba@kernel.org>
Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
 bpf@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
 Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
 Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
 "H. Peter Anvin" <hpa@zytor.com>,
 Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
 "Rafael J. Wysocki" <rafael@kernel.org>,
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 =?UTF-8?Q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>,
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 John Fastabend <john.fastabend@gmail.com>, Wei Fang <wei.fang@nxp.com>,
 Shenwei Wang <shenwei.wang@nxp.com>, Clark Wang <xiaoning.wang@nxp.com>,
 NXP Linux Team <linux-imx@nxp.com>, Jeroen de Borst <jeroendb@google.com>,
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 Shailend Chand <shailend@google.com>, Yisen Zhuang
 <yisen.zhuang@huawei.com>, Salil Mehta <salil.mehta@huawei.com>,
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 AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>,
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 "K. Y. Srinivasan" <kys@microsoft.com>,
 Haiyang Zhang <haiyangz@microsoft.com>, Wei Liu <wei.liu@kernel.org>,
 Dexuan Cui <decui@microsoft.com>, Jassi Brar <jaswinder.singh@linaro.org>,
 Ilias Apalodimas <ilias.apalodimas@linaro.org>,
 Alexandre Torgue <alexandre.torgue@foss.st.com>,
 Jose Abreu <joabreu@synopsys.com>,
 Maxime Coquelin <mcoquelin.stm32@gmail.com>,
 Siddharth Vadapalli <s-vadapalli@ti.com>,
 Ravi Gunasekaran <r-gunasekaran@ti.com>, Roger Quadros <rogerq@kernel.org>,
 Jiawen Wu <jiawenwu@trustnetic.com>, Mengyuan Lou
 <mengyuanlou@net-swift.com>, Ronak Doshi <doshir@vmware.com>,
 VMware PV-Drivers Reviewers <pv-drivers@vmware.com>,
 Ryder Lee <ryder.lee@mediatek.com>, Shayne Chen <shayne.chen@mediatek.com>,
 Kalle Valo <kvalo@kernel.org>, Juergen Gross <jgross@suse.com>,
 Stefano Stabellini <sstabellini@kernel.org>,
 Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>,
 Andrii Nakryiko <andrii@kernel.org>, Martin KaFai Lau
 <martin.lau@linux.dev>, Song Liu <song@kernel.org>,
 Yonghong Song <yonghong.song@linux.dev>, KP Singh <kpsingh@kernel.org>,
 Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>,
 Jiri Olsa <jolsa@kernel.org>, Stefan Hajnoczi <stefanha@redhat.com>,
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 =?UTF-8?Q?Micka=C3=ABl_Sala=C3=BCn?= <mic@digikod.net>,
 Nathan Chancellor <nathan@kernel.org>,
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References: <20231214020530.2267499-1-almasrymina@google.com>
 <20231214020530.2267499-3-almasrymina@google.com>
 <20231215185159.7bada9a7@kernel.org>
 <CAHS8izMcFWu7zSuX9q8QgVNLiOiE5RKsb_yh5LoTKA1K8FUu1w@mail.gmail.com>
From: David Ahern <dsahern@kernel.org>
In-Reply-To: <CAHS8izMcFWu7zSuX9q8QgVNLiOiE5RKsb_yh5LoTKA1K8FUu1w@mail.gmail.com>
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On 12/16/23 2:10 PM, Mina Almasry wrote:
> On Fri, Dec 15, 2023 at 6:52 PM Jakub Kicinski <kuba@kernel.org> wrote:
>>
>> On Wed, 13 Dec 2023 18:05:25 -0800 Mina Almasry wrote:
>>> +struct netmem {
>>> +     union {
>>> +             struct page page;
>>> +
>>> +             /* Stub to prevent compiler implicitly converting from page*
>>> +              * to netmem_t* and vice versa.
>>> +              *
>>> +              * Other memory type(s) net stack would like to support
>>> +              * can be added to this union.
>>> +              */
>>> +             void *addr;
>>> +     };
>>> +};
>>
>> My mind went to something like:
>>
>> typedef unsigned long __bitwise netmem_ref;
>>
>> instead. struct netmem does not exist, it's a handle which has
>> to be converted to a real type using a helper.
> 
> Sure thing I can do that. Is it better to do something like:
> 
> struct netmem_ref;
> 
> like in this patch:
> 
> https://lore.kernel.org/linux-mm/20221108194139.57604-1-torvalds@linux-foundation.org/
> 
> Asking because checkpatch tells me not to add typedefs to the kernel,
> but checkpatch can be ignored if you think it's OK.
> 
> Also with this approach I can't use container_of and I need to do a
> cast, I assume that's fine.
> 

Isn't that the whole point of this set - to introduce a new data type
and avoid casts?