netdev - [PATCH net-next v1 1/2] page_pool: reintroduce page_pool_unlink

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Date: Tue, 25 Jun 2024 12:55:21 -0700
From: David Wei <dw@...idwei.uk>
To: Michael Chan <michael.chan@...adcom.com>,
	Andy Gospodarek <andrew.gospodarek@...adcom.com>,
	Jesper Dangaard Brouer <hawk@...nel.org>,
	Ilias Apalodimas <ilias.apalodimas@...aro.org>,
	netdev@...r.kernel.org
Cc: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>
Subject: [PATCH net-next v1 1/2] page_pool: reintroduce page_pool_unlink_napi()

56ef27e3 unexported page_pool_unlink_napi() and renamed it to
page_pool_disable_direct_recycling(). This is because there was no
in-tree user of page_pool_unlink_napi().

Since then Rx queue API and an implementation in bnxt got merged. In the
bnxt implementation, it broadly follows the following steps: allocate
new queue memory + page pool, stop old rx queue, swap, then destroy old
queue memory + page pool. The existing NAPI instance is re-used.

The page pool to be destroyed is still linked to the re-used NAPI
instance. Freeing it as-is will trigger warnings in
page_pool_disable_direct_recycling(). In my initial patches I unlinked
very directly by setting pp.napi to NULL.

Instead, bring back page_pool_unlink_napi() and use that instead of
having a driver touch a core struct directly.

Suggested-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: David Wei <dw@...idwei.uk>
---
 include/net/page_pool/types.h | 5 +++++
 net/core/page_pool.c          | 6 ++++++
 2 files changed, 11 insertions(+)

diff --git a/include/net/page_pool/types.h b/include/net/page_pool/types.h
index 7e8477057f3d..aa3e615f1ae6 100644
--- a/include/net/page_pool/types.h
+++ b/include/net/page_pool/types.h
@@ -229,12 +229,17 @@ struct page_pool *page_pool_create_percpu(const struct page_pool_params *params,
 struct xdp_mem_info;
 
 #ifdef CONFIG_PAGE_POOL
+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 *),
 			   const struct xdp_mem_info *mem);
 void page_pool_put_page_bulk(struct page_pool *pool, void **data,
 			     int count);
 #else
+static inline void page_pool_unlink_napi(struct page_pool *pool)
+{
+}
+
 static inline void page_pool_destroy(struct page_pool *pool)
 {
 }
diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index 3927a0a7fa9a..ec274dde0e32 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -1021,6 +1021,11 @@ static void page_pool_disable_direct_recycling(struct page_pool *pool)
 	 */
 	WRITE_ONCE(pool->cpuid, -1);
 
+	page_pool_unlink_napi(pool);
+}
+
+void page_pool_unlink_napi(struct page_pool *pool)
+{
 	if (!pool->p.napi)
 		return;
 
@@ -1032,6 +1037,7 @@ static void page_pool_disable_direct_recycling(struct page_pool *pool)
 
 	WRITE_ONCE(pool->p.napi, NULL);
 }
+EXPORT_SYMBOL(page_pool_unlink_napi);
 
 void page_pool_destroy(struct page_pool *pool)
 {
-- 
2.43.0