Merge branch 'net-page_pool-remove-page_pool_release_page'

Jakub Kicinski says:

====================
net: page_pool: remove page_pool_release_page()

page_pool_return_page() is a historic artefact from before
recycling of pages attached to skbs was supported. Theoretical
uses for it may be thought up but in practice all existing
users can be converted to use skb_mark_for_recycle() instead.

This code was previously posted as part of the memory provider RFC.
https://lore.kernel.org/all/20230707183935.997267-1-kuba@kernel.org/
====================

Link: https://lore.kernel.org/r/20230720010409.1967072-1-kuba@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/networking/page_pool.rst

@@ -13,9 +13,9 @@ replacing dev_alloc_pages().
 
 API keeps track of in-flight pages, in order to let API user know
 when it is safe to free a page_pool object.  Thus, API users
-must run page_pool_release_page() when a page is leaving the page_pool or
-call page_pool_put_page() where appropriate in order to maintain correct
-accounting.
+must call page_pool_put_page() to free the page, or attach
+the page to a page_pool-aware objects like skbs marked with
+skb_mark_for_recycle().
 
 API user must call page_pool_put_page() once on a page, as it
 will either recycle the page, or in case of refcnt > 1, it will
@@ -87,9 +87,6 @@ a page will cause no race conditions is enough.
   must guarantee safe context (e.g NAPI), since it will recycle the page
   directly into the pool fast cache.
 
-* page_pool_release_page(): Unmap the page (if mapped) and account for it on
-  in-flight counters.
-
 * page_pool_dev_alloc_pages(): Get a page from the page allocator or page_pool
   caches.
 
@@ -194,7 +191,7 @@ NAPI poller
             if XDP_DROP:
                 page_pool_recycle_direct(page_pool, page);
         } else (packet_is_skb) {
-            page_pool_release_page(page_pool, page);
+            skb_mark_for_recycle(skb);
             new_page = page_pool_dev_alloc_pages(page_pool);
         }
     }

drivers/net/ethernet/engleder/tsnep_main.c

@@ -1333,7 +1333,7 @@ static void tsnep_rx_page(struct tsnep_rx *rx, struct napi_struct *napi,
 
 	skb = tsnep_build_skb(rx, page, length);
 	if (skb) {
-		page_pool_release_page(rx->page_pool, page);
+		skb_mark_for_recycle(skb);
 
 		rx->packets++;
 		rx->bytes += length;

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -5441,7 +5441,7 @@ static int stmmac_rx(struct stmmac_priv *priv, int limit, u32 queue)
 					priv->dma_conf.dma_buf_sz);
 
 			/* Data payload appended into SKB */
-			page_pool_release_page(rx_q->page_pool, buf->page);
+			skb_mark_for_recycle(skb);
 			buf->page = NULL;
 		}
 
@@ -5453,7 +5453,7 @@ static int stmmac_rx(struct stmmac_priv *priv, int limit, u32 queue)
 					priv->dma_conf.dma_buf_sz);
 
 			/* Data payload appended into SKB */
-			page_pool_release_page(rx_q->page_pool, buf->sec_page);
+			skb_mark_for_recycle(skb);
 			buf->sec_page = NULL;
 		}
 

include/net/page_pool.h

@@ -18,9 +18,8 @@
  *
  * API keeps track of in-flight pages, in-order to let API user know
  * when it is safe to dealloactor page_pool object.  Thus, API users
- * must make sure to call page_pool_release_page() when a page is
- * "leaving" the page_pool.  Or call page_pool_put_page() where
- * appropiate.  For maintaining correct accounting.
+ * must call page_pool_put_page() where appropriate and only attach
+ * the page to a page_pool-aware objects, like skbs marked for recycling.
  *
  * API user must only call page_pool_put_page() once on a page, as it
  * will either recycle the page, or in case of elevated refcnt, it
@@ -251,7 +250,6 @@ void page_pool_unlink_napi(struct page_pool *pool);
 void page_pool_destroy(struct page_pool *pool);
 void page_pool_use_xdp_mem(struct page_pool *pool, void (*disconnect)(void *),
 			   struct xdp_mem_info *mem);
-void page_pool_release_page(struct page_pool *pool, struct page *page);
 void page_pool_put_page_bulk(struct page_pool *pool, void **data,
 			     int count);
 #else
@@ -268,10 +266,6 @@ static inline void page_pool_use_xdp_mem(struct page_pool *pool,
 					 struct xdp_mem_info *mem)
 {
 }
-static inline void page_pool_release_page(struct page_pool *pool,
-					  struct page *page)
-{
-}
 
 static inline void page_pool_put_page_bulk(struct page_pool *pool, void **data,
 					   int count)

net/core/page_pool.c

@@ -492,7 +492,7 @@ static s32 page_pool_inflight(struct page_pool *pool)
  * a regular page (that will eventually be returned to the normal
  * page-allocator via put_page).
  */
-void page_pool_release_page(struct page_pool *pool, struct page *page)
+static void page_pool_return_page(struct page_pool *pool, struct page *page)
 {
 	dma_addr_t dma;
 	int count;
@@ -518,13 +518,6 @@ void page_pool_release_page(struct page_pool *pool, struct page *page)
 	 */
 	count = atomic_inc_return_relaxed(&pool->pages_state_release_cnt);
 	trace_page_pool_state_release(pool, page, count);
-}
-EXPORT_SYMBOL(page_pool_release_page);
-
-/* Return a page to the page allocator, cleaning up our state */
-static void page_pool_return_page(struct page_pool *pool, struct page *page)
-{
-	page_pool_release_page(pool, page);
 
 	put_page(page);
 	/* An optimization would be to call __free_pages(page, pool->p.order)
@@ -616,9 +609,7 @@ __page_pool_put_page(struct page_pool *pool, struct page *page,
 	 * will be invoking put_page.
 	 */
 	recycle_stat_inc(pool, released_refcnt);
-	/* Do not replace this with page_pool_return_page() */
-	page_pool_release_page(pool, page);
-	put_page(page);
+	page_pool_return_page(pool, page);
 
 	return NULL;
 }