[net-next v1 01/16] net: page_pool: factor out releasing DMA from releasing the page

Mina Almasry
2023-12-08T00:53:05Z

From: Jakub Kicinski <kuba@kernel.org>

Releasing the DMA mapping will be useful for other types
of pages, so factor it out. Make sure compiler inlines it,
to avoid any regressions.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Mina Almasry <almasrymina@google.com>

---

This is implemented by Jakub in his RFC:

https://lore.kernel.org/netdev/f8270765-a27b-6ccf-33ea-cda097168d79@redhat.com/T/

I take no credit for the idea or implementation. This is a critical
dependency of device memory TCP and thus I'm pulling it into this series
to make it revewable and mergable.

---
net/core/page_pool.c | 25 ++++++++++++++++---------
1 file changed, 16 insertions(+), 9 deletions(-)

diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index c2e7c9a6efbe..ca1b3b65c9b5 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -548,21 +548,16 @@ s32 page_pool_inflight(const struct page_pool *pool, bool strict)
return inflight;
}

-/* Disconnects a page (from a page_pool). API users can have a need
- * to disconnect a page (from a page_pool), to allow it to be used as
- * a regular page (that will eventually be returned to the normal
- * page-allocator via put_page).
- */
-static void page_pool_return_page(struct page_pool *pool, struct page *page)
+static __always_inline
+void __page_pool_release_page_dma(struct page_pool *pool, struct page *page)
{
dma_addr_t dma;
- int count;

if (!(pool->p.flags & PP_FLAG_DMA_MAP))
/* Always account for inflight pages, even if we didn't
* map them
*/
- goto skip_dma_unmap;
+ return;

dma = page_pool_get_dma_addr(page);

@@ -571,7 +566,19 @@ static void page_pool_return_page(struct page_pool *pool, struct page *page)
PAGE_SIZE << pool->p.order, pool->p.dma_dir,
DMA_ATTR_SKIP_CPU_SYNC | DMA_ATTR_WEAK_ORDERING);
page_pool_set_dma_addr(page, 0);
-skip_dma_unmap:
+}
+
+/* Disconnects a page (from a page_pool). API users can have a need
+ * to disconnect a page (from a page_pool), to allow it to be used as
+ * a regular page (that will eventually be returned to the normal
+ * page-allocator via put_page).
+ */
+void page_pool_return_page(struct page_pool *pool, struct page *page)
+{
+ int count;
+
+ __page_pool_release_page_dma(pool, page);
+
page_pool_clear_pp_info(page);

/* This may be the last page returned, releasing the pool, so
--
2.43.0.472.g3155946c3a-goog