netdev - [RFC net-next v1 5/6] net: page_pool: convert refcounting helpers to nmdesc

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Message-ID: <7be7a705b9bac445e40c35cd227a4d5486d95dc9.1754929026.git.asml.silence@gmail.com>
Date: Mon, 11 Aug 2025 17:29:42 +0100
From: Pavel Begunkov <asml.silence@...il.com>
To: netdev@...r.kernel.org
Cc: Jakub Kicinski <kuba@...nel.org>,
	Eric Dumazet <edumazet@...gle.com>,
	Paolo Abeni <pabeni@...hat.com>,
	davem@...emloft.net,
	sdf@...ichev.me,
	almasrymina@...gle.com,
	dw@...idwei.uk,
	Jesper Dangaard Brouer <hawk@...nel.org>,
	Ilias Apalodimas <ilias.apalodimas@...aro.org>,
	Byungchul Park <byungchul@...com>,
	asml.silence@...il.com
Subject: [RFC net-next v1 5/6] net: page_pool: convert refcounting helpers to nmdesc

Use netmem descriptors for the basic buffer refcounting helpers and use
them to implement all other variants. This way netmem type aware helpers
can avoid intermediate netmem casting and bit masking/unmasking.

Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
---
 include/net/netmem.h            |  5 -----
 include/net/page_pool/helpers.h | 29 ++++++++++++++++++++++-------
 net/core/devmem.c               |  5 -----
 3 files changed, 22 insertions(+), 17 deletions(-)

diff --git a/include/net/netmem.h b/include/net/netmem.h
index ca6d5d151acc..7b5f1427f272 100644
--- a/include/net/netmem.h
+++ b/include/net/netmem.h
@@ -324,11 +324,6 @@ static inline struct page_pool *netmem_get_pp(netmem_ref netmem)
 	return netmem_to_nmdesc(netmem)->pp;
 }
 
-static inline atomic_long_t *netmem_get_pp_ref_count_ref(netmem_ref netmem)
-{
-	return &netmem_to_nmdesc(netmem)->pp_ref_count;
-}
-
 static inline bool netmem_is_pref_nid(netmem_ref netmem, int pref_nid)
 {
 	/* NUMA node preference only makes sense if we're allocating
diff --git a/include/net/page_pool/helpers.h b/include/net/page_pool/helpers.h
index a9774d582933..bc54040186d9 100644
--- a/include/net/page_pool/helpers.h
+++ b/include/net/page_pool/helpers.h
@@ -234,9 +234,14 @@ page_pool_get_dma_dir(const struct page_pool *pool)
 	return pool->p.dma_dir;
 }
 
+static inline void page_pool_fragment_nmdesc(struct netmem_desc *desc, long nr)
+{
+	atomic_long_set(&desc->pp_ref_count, nr);
+}
+
 static inline void page_pool_fragment_netmem(netmem_ref netmem, long nr)
 {
-	atomic_long_set(netmem_get_pp_ref_count_ref(netmem), nr);
+	page_pool_fragment_nmdesc(netmem_to_nmdesc(netmem), nr);
 }
 
 /**
@@ -259,12 +264,12 @@ static inline void page_pool_fragment_netmem(netmem_ref netmem, long nr)
  */
 static inline void page_pool_fragment_page(struct page *page, long nr)
 {
-	page_pool_fragment_netmem(page_to_netmem(page), nr);
+	page_pool_fragment_nmdesc(pp_page_to_nmdesc(page), nr);
 }
 
-static inline long page_pool_unref_netmem(netmem_ref netmem, long nr)
+static inline long page_pool_unref_nmdesc(struct netmem_desc *desc, long nr)
 {
-	atomic_long_t *pp_ref_count = netmem_get_pp_ref_count_ref(netmem);
+	atomic_long_t *pp_ref_count = &desc->pp_ref_count;
 	long ret;
 
 	/* If nr == pp_ref_count then we have cleared all remaining
@@ -307,19 +312,29 @@ static inline long page_pool_unref_netmem(netmem_ref netmem, long nr)
 	return ret;
 }
 
+static inline long page_pool_unref_netmem(netmem_ref netmem, long nr)
+{
+	return page_pool_unref_nmdesc(netmem_to_nmdesc(netmem), nr);
+}
+
 static inline long page_pool_unref_page(struct page *page, long nr)
 {
-	return page_pool_unref_netmem(page_to_netmem(page), nr);
+	return page_pool_unref_nmdesc(pp_page_to_nmdesc(page), nr);
+}
+
+static inline void page_pool_ref_nmdesc(struct netmem_desc *desc)
+{
+	atomic_long_inc(&desc->pp_ref_count);
 }
 
 static inline void page_pool_ref_netmem(netmem_ref netmem)
 {
-	atomic_long_inc(netmem_get_pp_ref_count_ref(netmem));
+	page_pool_ref_nmdesc(netmem_to_nmdesc(netmem));
 }
 
 static inline void page_pool_ref_page(struct page *page)
 {
-	page_pool_ref_netmem(page_to_netmem(page));
+	page_pool_ref_nmdesc(pp_page_to_nmdesc(page));
 }
 
 static inline bool page_pool_unref_and_test(netmem_ref netmem)
diff --git a/net/core/devmem.c b/net/core/devmem.c
index 24c591ab38ae..e084dad11506 100644
--- a/net/core/devmem.c
+++ b/net/core/devmem.c
@@ -440,14 +440,9 @@ void mp_dmabuf_devmem_destroy(struct page_pool *pool)
 
 bool mp_dmabuf_devmem_release_page(struct page_pool *pool, netmem_ref netmem)
 {
-	long refcount = atomic_long_read(netmem_get_pp_ref_count_ref(netmem));
-
 	if (WARN_ON_ONCE(!netmem_is_net_iov(netmem)))
 		return false;
 
-	if (WARN_ON_ONCE(refcount != 1))
-		return false;
-
 	page_pool_clear_pp_info(netmem);
 
 	net_devmem_free_dmabuf(netmem_to_net_iov(netmem));
-- 
2.49.0