We can save a couple more function calls in the Page Pool code if we
check for dma_need_sync() earlier, just when we test pp->p.dma_sync.
Move both these checks into an inline wrapper and call the PP wrapper
over the generic DMA sync function only when both are true.
You can't cache the result of dma_need_sync() in &page_pool, as it may
change anytime if an SWIOTLB buffer is allocated or mapped.

Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
---
 net/core/page_pool.c | 33 +++++++++++++++++++--------------
 1 file changed, 19 insertions(+), 14 deletions(-)

diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index e680c4af2745..84132c978773 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -399,16 +399,26 @@ static struct page *__page_pool_get_cached(struct page_pool *pool)
 	return page;
 }
 
-static void page_pool_dma_sync_for_device(const struct page_pool *pool,
-					  const struct page *page,
-					  unsigned int dma_sync_size)
+static void __page_pool_dma_sync_for_device(const struct page_pool *pool,
+					    const struct page *page,
+					    u32 dma_sync_size)
 {
+#ifdef CONFIG_DMA_NEED_SYNC
 	dma_addr_t dma_addr = page_pool_get_dma_addr(page);
 
 	dma_sync_size = min(dma_sync_size, pool->p.max_len);
-	dma_sync_single_range_for_device(pool->p.dev, dma_addr,
-					 pool->p.offset, dma_sync_size,
-					 pool->p.dma_dir);
+	__dma_sync_single_for_device(pool->p.dev, dma_addr + pool->p.offset,
+				     dma_sync_size, pool->p.dma_dir);
+#endif
+}
+
+static __always_inline void
+page_pool_dma_sync_for_device(const struct page_pool *pool,
+			      const struct page *page,
+			      u32 dma_sync_size)
+{
+	if (pool->dma_sync && dma_dev_need_sync(pool->p.dev))
+		__page_pool_dma_sync_for_device(pool, page, dma_sync_size);
 }
 
 static bool page_pool_dma_map(struct page_pool *pool, struct page *page)
@@ -430,8 +440,7 @@ static bool page_pool_dma_map(struct page_pool *pool, struct page *page)
 	if (page_pool_set_dma_addr(page, dma))
 		goto unmap_failed;
 
-	if (pool->dma_sync)
-		page_pool_dma_sync_for_device(pool, page, pool->p.max_len);
+	page_pool_dma_sync_for_device(pool, page, pool->p.max_len);
 
 	return true;
 
@@ -701,9 +710,7 @@ __page_pool_put_page(struct page_pool *pool, struct page *page,
 	if (likely(__page_pool_page_can_be_recycled(page))) {
 		/* Read barrier done in page_ref_count / READ_ONCE */
 
-		if (pool->dma_sync)
-			page_pool_dma_sync_for_device(pool, page,
-						      dma_sync_size);
+		page_pool_dma_sync_for_device(pool, page, dma_sync_size);
 
 		if (allow_direct && page_pool_recycle_in_cache(page, pool))
 			return NULL;
@@ -842,9 +849,7 @@ static struct page *page_pool_drain_frag(struct page_pool *pool,
 		return NULL;
 
 	if (__page_pool_page_can_be_recycled(page)) {
-		if (pool->dma_sync)
-			page_pool_dma_sync_for_device(pool, page, -1);
-
+		page_pool_dma_sync_for_device(pool, page, -1);
 		return page;
 	}
 
-- 
2.45.0

The first hunk here fails when trying to apply it to the 6.9-rc6
based dma-mapping for-next tree.

Should I go ahead and just apply the first three patches?  Or do
we need a shared branch with something?

From: Christoph Hellwig <hch@lst.de>
Date: Mon, 6 May 2024 13:50:43 +0200

> The first hunk here fails when trying to apply it to the 6.9-rc6
> based dma-mapping for-next tree.
> 
> Should I go ahead and just apply the first three patches?  Or do
> we need a shared branch with something?

My CI fails now fails to compile this patch when !HAS_DMA. Let me fix
this, rebase on top of your tree and resend? We'll resolve this conflict
in linux-next then.

Thanks,
Olek

On Tue, May 07, 2024 at 11:51:46AM +0200, Alexander Lobakin wrote:
> My CI fails now fails to compile this patch when !HAS_DMA. Let me fix
> this, rebase on top of your tree and resend?

Ok.