linux-kernel - Re: [RFC PATCH net-next v8 02/14] net: page_pool: create hooks for custom page providers

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Message-ID: <ZjpVfPqGNfE5N4bl@infradead.org>
Date: Tue, 7 May 2024 09:23:24 -0700
From: Christoph Hellwig <hch@...radead.org>
To: Jason Gunthorpe <jgg@...pe.ca>
Cc: Pavel Begunkov <asml.silence@...il.com>,
	Christoph Hellwig <hch@...radead.org>,
	Mina Almasry <almasrymina@...gle.com>, netdev@...r.kernel.org,
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Subject: Re: [RFC PATCH net-next v8 02/14] net: page_pool: create hooks for
 custom page providers

On Tue, May 07, 2024 at 01:18:57PM -0300, Jason Gunthorpe wrote:
> On Tue, May 07, 2024 at 05:05:12PM +0100, Pavel Begunkov wrote:
> > > even in tree if you give them enough rope, and they should not have
> > > that rope when the only sensible options are page/folio based kernel
> > > memory (incuding large/huge folios) and dmabuf.
> > 
> > I believe there is at least one deep confusion here, considering you
> > previously mentioned Keith's pre-mapping patches. The "hooks" are not
> > that about in what format you pass memory, it's arguably the least
> > interesting part for page pool, more or less it'd circulate whatever
> > is given. It's more of how to have a better control over buffer lifetime
> > and implement a buffer pool passing data to users and empty buffers
> > back.
> 
> Isn't that more or less exactly what dmabuf is? Why do you need
> another almost dma-buf thing for another project?

That's the exact point I've been making since the last round of
the series.  We don't need to reinvent dmabuf poorly in every
subsystem, but instead fix the odd parts in it and make it suitable
for everyone.