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Date:   Tue, 12 Dec 2023 05:07:34 -0800
From:   Christoph Hellwig <hch@infradead.org>
To:     Jason Gunthorpe <jgg@nvidia.com>
Cc:     Mina Almasry <almasrymina@google.com>,
        Shailend Chand <shailend@google.com>, netdev@vger.kernel.org,
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        Eric Dumazet <edumazet@google.com>,
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        Jesper Dangaard Brouer <hawk@kernel.org>,
        Ilias Apalodimas <ilias.apalodimas@linaro.org>,
        Arnd Bergmann <arnd@arndb.de>,
        David Ahern <dsahern@kernel.org>,
        Willem de Bruijn <willemdebruijn.kernel@gmail.com>,
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        Sumit Semwal <sumit.semwal@linaro.org>,
        Christian =?iso-8859-1?Q?K=F6nig?= <christian.koenig@amd.com>,
        Yunsheng Lin <linyunsheng@huawei.com>,
        Harshitha Ramamurthy <hramamurthy@google.com>,
        Shakeel Butt <shakeelb@google.com>,
        Willem de Bruijn <willemb@google.com>,
        Kaiyuan Zhang <kaiyuanz@google.com>,
        Christoph Hellwig <hch@infradead.org>
Subject: Re: [net-next v1 08/16] memory-provider: dmabuf devmem memory
 provider
Message-ID: <ZXhbFi42YClOVhQ7@infradead.org>
References: <20231208005250.2910004-1-almasrymina@google.com>
 <20231208005250.2910004-9-almasrymina@google.com>
 <20231212122535.GA3029808@nvidia.com>
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On Tue, Dec 12, 2023 at 08:25:35AM -0400, Jason Gunthorpe wrote:
> > +static inline struct page_pool_iov *page_to_page_pool_iov(struct page *page)
> > +{
> > +	if (page_is_page_pool_iov(page))
> > +		return (struct page_pool_iov *)((unsigned long)page & ~PP_IOV);
> > +
> > +	DEBUG_NET_WARN_ON_ONCE(true);
> > +	return NULL;
> > +}
> 
> We already asked not to do this, please do not allocate weird things
> can call them 'struct page' when they are not. It undermines the
> maintainability of the mm to have things mis-typed like
> this. Introduce a new type for your thing so the compiler can check it
> properly.

Yes.  Or even better avoid this mess entirely..