On 2024-03-17 19:02, Christoph Hellwig wrote:

On Mon, Mar 04, 2024 at 06:01:37PM -0800, Mina Almasry wrote:

quoted

From: Jakub Kicinski <kuba@kernel.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.

I'm working on a similar proposal for zero copy Rx but to host memory
and depend on this memory provider API.

Jakub also designed this API for hugepages too IIRC. Basically there's
going to be at least three fancy ways of providing pages (one of which
isn't actually pages, hence the merged netmem_t series) to drivers.