netdev - [PATCH net-next 3/4] page_pool: Restructure __page_pool_put

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Date:   Tue, 22 Oct 2019 04:44:24 +0000
From:   Saeed Mahameed <saeedm@...lanox.com>
To:     "David S. Miller" <davem@...emloft.net>,
        Jesper Dangaard Brouer <brouer@...hat.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        "ilias.apalodimas@...aro.org" <ilias.apalodimas@...aro.org>,
        Saeed Mahameed <saeedm@...lanox.com>
Subject: [PATCH net-next 3/4] page_pool: Restructure __page_pool_put_page()

From: Jonathan Lemon <jonathan.lemon@...il.com>

1) Rename functions to reflect what they are actually doing.

2) Unify the condition to keep a page.

3) When page can't be kept in cache, fallback to releasing page to page
allocator in one place, instead of calling it from multiple conditions,
and reuse __page_pool_return_page().

Signed-off-by: Jonathan Lemon <jonathan.lemon@...il.com>
Signed-off-by: Saeed Mahameed <saeedm@...lanox.com>
---
 net/core/page_pool.c | 38 +++++++++++++++++++-------------------
 1 file changed, 19 insertions(+), 19 deletions(-)

diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index 8120aec999ce..65680aaa0818 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -258,6 +258,7 @@ static bool __page_pool_recycle_into_ring(struct page_pool *pool,
 				   struct page *page)
 {
 	int ret;
+
 	/* BH protection not needed if current is serving softirq */
 	if (in_serving_softirq())
 		ret = ptr_ring_produce(&pool->ring, page);
@@ -272,8 +273,8 @@ static bool __page_pool_recycle_into_ring(struct page_pool *pool,
  *
  * Caller must provide appropriate safe context.
  */
-static bool __page_pool_recycle_direct(struct page *page,
-				       struct page_pool *pool)
+static bool __page_pool_recycle_into_cache(struct page *page,
+					   struct page_pool *pool)
 {
 	if (unlikely(pool->alloc.count == PP_ALLOC_CACHE_SIZE))
 		return false;
@@ -283,15 +284,18 @@ static bool __page_pool_recycle_direct(struct page *page,
 	return true;
 }
 
-/* page is NOT reusable when:
- * 1) allocated when system is under some pressure. (page_is_pfmemalloc)
- * 2) belongs to a different NUMA node than pool->p.nid.
+/* Keep page in caches only if page:
+ * 1) wasn't allocated when system is under some pressure (page_is_pfmemalloc).
+ * 2) belongs to pool's numa node (pool->p.nid).
+ * 3) refcount is 1 (owned by page pool).
  *
  * To update pool->p.nid users must call page_pool_update_nid.
  */
-static bool pool_page_reusable(struct page_pool *pool, struct page *page)
+static bool page_pool_keep_page(struct page_pool *pool, struct page *page)
 {
-	return !page_is_pfmemalloc(page) && page_to_nid(page) == pool->p.nid;
+	return !page_is_pfmemalloc(page) &&
+	       page_to_nid(page) == pool->p.nid &&
+	       page_ref_count(page) == 1;
 }
 
 void __page_pool_put_page(struct page_pool *pool,
@@ -300,22 +304,19 @@ void __page_pool_put_page(struct page_pool *pool,
 	/* This allocator is optimized for the XDP mode that uses
 	 * one-frame-per-page, but have fallbacks that act like the
 	 * regular page allocator APIs.
-	 *
-	 * refcnt == 1 means page_pool owns page, and can recycle it.
 	 */
-	if (likely(page_ref_count(page) == 1 &&
-		   pool_page_reusable(pool, page))) {
+
+	if (likely(page_pool_keep_page(pool, page))) {
 		/* Read barrier done in page_ref_count / READ_ONCE */
 
 		if (allow_direct && in_serving_softirq())
-			if (__page_pool_recycle_direct(page, pool))
+			if (__page_pool_recycle_into_cache(page, pool))
 				return;
 
-		if (!__page_pool_recycle_into_ring(pool, page)) {
-			/* Cache full, fallback to free pages */
-			__page_pool_return_page(pool, page);
-		}
-		return;
+		if (__page_pool_recycle_into_ring(pool, page))
+			return;
+
+		/* Cache full, fallback to return pages */
 	}
 	/* Fallback/non-XDP mode: API user have elevated refcnt.
 	 *
@@ -330,8 +331,7 @@ void __page_pool_put_page(struct page_pool *pool,
 	 * doing refcnt based recycle tricks, meaning another process
 	 * will be invoking put_page.
 	 */
-	__page_pool_clean_page(pool, page);
-	put_page(page);
+	__page_pool_return_page(pool, page);
 }
 EXPORT_SYMBOL(__page_pool_put_page);
 
-- 
2.21.0