netdev - [RFC PATCH v3 01/12] net: page_pool: factor out releasing DMA from releasing the page

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Date: Sun,  5 Nov 2023 18:44:00 -0800
From: Mina Almasry <almasrymina@...gle.com>
To: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-arch@...r.kernel.org, linux-kselftest@...r.kernel.org, 
	linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
	linaro-mm-sig@...ts.linaro.org
Cc: Mina Almasry <almasrymina@...gle.com>, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	Jesper Dangaard Brouer <hawk@...nel.org>, Ilias Apalodimas <ilias.apalodimas@...aro.org>, 
	Arnd Bergmann <arnd@...db.de>, David Ahern <dsahern@...nel.org>, 
	Willem de Bruijn <willemdebruijn.kernel@...il.com>, Shuah Khan <shuah@...nel.org>, 
	Sumit Semwal <sumit.semwal@...aro.org>, 
	"Christian König" <christian.koenig@....com>, Shakeel Butt <shakeelb@...gle.com>, 
	Jeroen de Borst <jeroendb@...gle.com>, Praveen Kaligineedi <pkaligineedi@...gle.com>
Subject: [RFC PATCH v3 01/12] net: page_pool: factor out releasing DMA from
 releasing the page

From: Jakub Kicinski <kuba@...nel.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@...nel.org>
Signed-off-by: Mina Almasry <almasrymina@...gle.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 5e409b98aba0..578b6f2eeb46 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -514,21 +514,16 @@ static s32 page_pool_inflight(struct page_pool *pool)
 	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);
 
@@ -537,7 +532,19 @@ 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
-- 
2.42.0.869.gea05f2083d-goog