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Date: Tue, 14 Nov 2023 17:25:34 -0500
From: Jakub Kicinski <kuba@kernel.org>
To: Yunsheng Lin <linyunsheng@huawei.com>
Cc: Mina Almasry <almasrymina@google.com>, <davem@davemloft.net>,
 <pabeni@redhat.com>, <netdev@vger.kernel.org>,
 <linux-kernel@vger.kernel.org>, Willem de Bruijn <willemb@google.com>,
 Kaiyuan Zhang <kaiyuanz@google.com>, Jesper Dangaard Brouer
 <hawk@kernel.org>, Ilias Apalodimas <ilias.apalodimas@linaro.org>, Eric
 Dumazet <edumazet@google.com>, Christian =?UTF-8?B?S8O2bmln?=
 <christian.koenig@amd.com>, Jason Gunthorpe <jgg@nvidia.com>, Matthew
 Wilcox <willy@infradead.org>, Linux-MM <linux-mm@kvack.org>
Subject: Re: [PATCH RFC 3/8] memory-provider: dmabuf devmem memory provider
Message-ID: <20231114172534.124f544c@kernel.org>
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References: <20231113130041.58124-1-linyunsheng@huawei.com>
	<20231113130041.58124-4-linyunsheng@huawei.com>
	<CAHS8izMjmj0DRT_vjzVq5HMQyXtZdVK=o4OP0gzbaN=aJdQ3ig@mail.gmail.com>
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On Tue, 14 Nov 2023 16:23:29 +0800 Yunsheng Lin wrote:
> I would expect net stack, page pool, driver still see the 'struct page',
> only memory provider see the specific struct for itself, for the above,
> devmem memory provider sees the 'struct page_pool_iov'.

You can't lie to the driver that an _iov is a page either.
The driver must explicitly "opt-in" to using the _iov variant,
by calling the _iov set of APIs.

Only drivers which can support header-data split can reasonably
use the _iov API, for data pages.