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Subject: [PATCH RFC net-next 1/3] net: page_pool: refactor dma_map into own
 function page_pool_dma_map
From:   Jesper Dangaard Brouer <brouer@redhat.com>
To:     Mel Gorman <mgorman@techsingularity.net>, linux-mm@kvack.org
Cc:     Jesper Dangaard Brouer <brouer@redhat.com>, chuck.lever@oracle.com,
        netdev@vger.kernel.org, linux-nfs@vger.kernel.org,
        linux-kernel@vger.kernel.org
Date:   Wed, 24 Feb 2021 19:56:41 +0100
Message-ID: <161419300107.2718959.18302883670835746249.stgit@firesoul>
In-Reply-To: <161419296941.2718959.12575257358107256094.stgit@firesoul>
References: <161419296941.2718959.12575257358107256094.stgit@firesoul>
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In preparation for next patch, move the dma mapping into its own
function, as this will make it easier to follow the changes.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
 net/core/page_pool.c |   49 +++++++++++++++++++++++++++++--------------------
 1 file changed, 29 insertions(+), 20 deletions(-)

diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index ad8b0707af04..50d52aa6fbeb 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -180,6 +180,31 @@ static void page_pool_dma_sync_for_device(struct page_pool *pool,
 					 pool->p.dma_dir);
 }
 
+static struct page * page_pool_dma_map(struct page_pool *pool,
+				       struct page *page)
+{
+	dma_addr_t dma;
+
+	/* Setup DMA mapping: use 'struct page' area for storing DMA-addr
+	 * since dma_addr_t can be either 32 or 64 bits and does not always fit
+	 * into page private data (i.e 32bit cpu with 64bit DMA caps)
+	 * This mapping is kept for lifetime of page, until leaving pool.
+	 */
+	dma = dma_map_page_attrs(pool->p.dev, page, 0,
+				 (PAGE_SIZE << pool->p.order),
+				 pool->p.dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
+	if (dma_mapping_error(pool->p.dev, dma)) {
+		put_page(page);
+		return NULL;
+	}
+	page->dma_addr = dma;
+
+	if (pool->p.flags & PP_FLAG_DMA_SYNC_DEV)
+		page_pool_dma_sync_for_device(pool, page, pool->p.max_len);
+
+	return page;
+}
+
 /* slow path */
 noinline
 static struct page *__page_pool_alloc_pages_slow(struct page_pool *pool,
@@ -187,7 +212,6 @@ static struct page *__page_pool_alloc_pages_slow(struct page_pool *pool,
 {
 	struct page *page;
 	gfp_t gfp = _gfp;
-	dma_addr_t dma;
 
 	/* We could always set __GFP_COMP, and avoid this branch, as
 	 * prep_new_page() can handle order-0 with __GFP_COMP.
@@ -211,27 +235,12 @@ static struct page *__page_pool_alloc_pages_slow(struct page_pool *pool,
 	if (!page)
 		return NULL;
 
-	if (!(pool->p.flags & PP_FLAG_DMA_MAP))
-		goto skip_dma_map;
-
-	/* Setup DMA mapping: use 'struct page' area for storing DMA-addr
-	 * since dma_addr_t can be either 32 or 64 bits and does not always fit
-	 * into page private data (i.e 32bit cpu with 64bit DMA caps)
-	 * This mapping is kept for lifetime of page, until leaving pool.
-	 */
-	dma = dma_map_page_attrs(pool->p.dev, page, 0,
-				 (PAGE_SIZE << pool->p.order),
-				 pool->p.dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
-	if (dma_mapping_error(pool->p.dev, dma)) {
-		put_page(page);
-		return NULL;
+	if (pool->p.flags & PP_FLAG_DMA_MAP) {
+		page = page_pool_dma_map(pool, page);
+		if (!page)
+			return NULL;
 	}
-	page->dma_addr = dma;
-
-	if (pool->p.flags & PP_FLAG_DMA_SYNC_DEV)
-		page_pool_dma_sync_for_device(pool, page, pool->p.max_len);
 
-skip_dma_map:
 	/* Track how many pages are held 'in-flight' */
 	pool->pages_state_hold_cnt++;