netdev - Re: [RFC PATCH net-next v6 02/15] net: page_pool: create hooks for custom page providers

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Date: Sun, 17 Mar 2024 19:02:52 -0700
From: Christoph Hellwig <hch@...radead.org>
To: Mina Almasry <almasrymina@...gle.com>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
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Subject: Re: [RFC PATCH net-next v6 02/15] net: page_pool: create hooks for
 custom page providers

On Mon, Mar 04, 2024 at 06:01:37PM -0800, Mina Almasry wrote:
> From: Jakub Kicinski <kuba@...nel.org>
> 
> The page providers which try to reuse the same pages will
> need to hold onto the ref, even if page gets released from
> the pool - as in releasing the page from the pp just transfers
> the "ownership" reference from pp to the provider, and provider
> will wait for other references to be gone before feeding this
> page back into the pool.

The word hook always rings a giant warning bell for me, and looking into
this series I am concerned indeed.

The only provider provided here is the dma-buf one, and that basically
is the only sensible one for the documented design.  So instead of
adding hooks that random proprietary crap can hook into, why not hard
code the dma buf provide and just use a flag?  That'll also avoid
expensive indirect calls.