netdev - [net-next PATCH 0/2] Fix page_pool API and dma address storage

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Date:   Mon, 11 Feb 2019 17:06:41 +0100
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     netdev@...r.kernel.org, linux-mm@...ck.org
Cc:     Toke Høiland-Jørgensen <toke@...e.dk>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        willy@...radead.org, Saeed Mahameed <saeedm@...lanox.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        mgorman@...hsingularity.net,
        "David S. Miller" <davem@...emloft.net>,
        Tariq Toukan <tariqt@...lanox.com>
Subject: [net-next PATCH 0/2] Fix page_pool API and dma address storage

As pointed out by David Miller in [1] the current page_pool implementation
stores dma_addr_t in page->private. This won't work on 32-bit platforms with
64-bit DMA addresses since the page->private is an unsigned long and the
dma_addr_t a u64.

Since no driver is yet using the DMA mapping capabilities of the API let's
fix this by storing the information in 'struct page' and use that to store
and retrieve DMA addresses from network drivers.

As long as the addresses returned from dma_map_page() are aligned the first
bit, used by the compound pages code should not be set.

Ilias tested this on Espressobin driver mvneta, for which we have patches
for using the DMA API of page_pool.

[1]: https://lore.kernel.org/netdev/20181207.230655.1261252486319967024.davem@davemloft.net/

Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@...aro.org>

---
Question: Who of the maintainers MM or netdev will take these changes?

---

Ilias Apalodimas (1):
      net: page_pool: don't use page->private to store dma_addr_t

Jesper Dangaard Brouer (1):
      mm: add dma_addr_t to struct page

 include/linux/mm_types.h |    8 ++++++++
 net/core/page_pool.c     |   13 +++++++++----
 2 files changed, 17 insertions(+), 4 deletions(-)

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