[PATCH RFC V2 net-next 1/2] net: page_pool: refactor dma_map into own function page_pool_dma_map

[Jesper Dangaard Brouer <brouer@redhat.com>]

In preparation for next patch, move the dma mapping into its own
function, as this will make it easier to follow the changes.

V2: make page_pool_dma_map return boolean (Ilias)

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
 net/core/page_pool.c |   45 ++++++++++++++++++++++++++-------------------
 1 file changed, 26 insertions(+), 19 deletions(-)

diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index ad8b0707af04..a26f2ceb6a87 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -180,14 +180,37 @@ static void page_pool_dma_sync_for_device(struct page_pool *pool,
 					 pool->p.dma_dir);
 }
 
+static bool 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))
+		return false;
+
+	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 true;
+}
+
 /* slow path */
 noinline
 static struct page *__page_pool_alloc_pages_slow(struct page_pool *pool,
 						 gfp_t _gfp)
 {
+	unsigned int pp_flags = pool->p.flags;
 	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.
@@ -211,30 +234,14 @@ 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)) {
+	if (pp_flags & PP_FLAG_DMA_MAP &&
+	    unlikely(!page_pool_dma_map(pool, page))) {
 		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);
-
-skip_dma_map:
 	/* Track how many pages are held 'in-flight' */
 	pool->pages_state_hold_cnt++;
-
 	trace_page_pool_state_hold(pool, page, pool->pages_state_hold_cnt);
 
 	/* When page just alloc'ed is should/must have refcnt 1. */