[PATCH v7 07/15] net: page_pool: introduce page_pool_mp_return_in_cache

[David Wei <dw@davidwei.uk>]

From: Pavel Begunkov <asml.silence@gmail.com>

Add a helper that allows a page pool memory provider to efficiently
return a netmem off the allocation callback.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: David Wei <dw@davidwei.uk>
---
 include/net/page_pool/memory_provider.h |  4 ++++
 net/core/page_pool.c                    | 19 +++++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/include/net/page_pool/memory_provider.h b/include/net/page_pool/memory_provider.h
index 83d7eec0058d..352b3a35d31c 100644
--- a/include/net/page_pool/memory_provider.h
+++ b/include/net/page_pool/memory_provider.h
@@ -1,3 +1,5 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
 #ifndef _NET_PAGE_POOL_MEMORY_PROVIDER_H
 #define _NET_PAGE_POOL_MEMORY_PROVIDER_H
 
@@ -7,4 +9,6 @@ int page_pool_mp_init_paged_area(struct page_pool *pool,
 void page_pool_mp_release_area(struct page_pool *pool,
 				struct net_iov_area *area);
 
+void page_pool_mp_return_in_cache(struct page_pool *pool, netmem_ref netmem);
+
 #endif
diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index 8bd4a3c80726..9078107c906d 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -1213,3 +1213,22 @@ void page_pool_mp_release_area(struct page_pool *pool,
 		page_pool_release_page_dma(pool, net_iov_to_netmem(niov));
 	}
 }
+
+/*
+ * page_pool_mp_return_in_cache() - return a netmem to the allocation cache.
+ * @pool:	pool from which pages were allocated
+ * @netmem:	netmem to return
+ *
+ * Return already allocated and accounted netmem to the page pool's allocation
+ * cache. The function doesn't provide synchronisation and must only be called
+ * from the napi context.
+ */
+void page_pool_mp_return_in_cache(struct page_pool *pool, netmem_ref netmem)
+{
+	if (WARN_ON_ONCE(pool->alloc.count >= PP_ALLOC_CACHE_REFILL))
+		return;
+
+	page_pool_dma_sync_for_device(pool, netmem, -1);
+	page_pool_fragment_netmem(netmem, 1);
+	pool->alloc.cache[pool->alloc.count++] = netmem;
+}
-- 
2.43.5