netdev - [PATCH v3 net-next 1/3] net: add a new @alloc parameter to napi_skb_cache

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Message-ID: <20251116202717.1542829-2-edumazet@google.com>
Date: Sun, 16 Nov 2025 20:27:15 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: Simon Horman <horms@...nel.org>, Kuniyuki Iwashima <kuniyu@...gle.com>, 
	Jason Xing <kerneljasonxing@...il.com>, netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH v3 net-next 1/3] net: add a new @alloc parameter to napi_skb_cache_get()

We want to be able in the series last patch to get an skb from
napi_skb_cache from process context, if there is one available.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/core/skbuff.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index f34372666e67cee5329d3ba1d3c86f8622facac3..88b5530f9c460d86e12c98e410774444367e0404 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -280,17 +280,18 @@ EXPORT_SYMBOL(__netdev_alloc_frag_align);
  */
 static u32 skbuff_cache_size __read_mostly;
 
-static struct sk_buff *napi_skb_cache_get(void)
+static struct sk_buff *napi_skb_cache_get(bool alloc)
 {
 	struct napi_alloc_cache *nc = this_cpu_ptr(&napi_alloc_cache);
 	struct sk_buff *skb;
 
 	local_lock_nested_bh(&napi_alloc_cache.bh_lock);
 	if (unlikely(!nc->skb_count)) {
-		nc->skb_count = kmem_cache_alloc_bulk(net_hotdata.skbuff_cache,
-						      GFP_ATOMIC | __GFP_NOWARN,
-						      NAPI_SKB_CACHE_BULK,
-						      nc->skb_cache);
+		if (alloc)
+			nc->skb_count = kmem_cache_alloc_bulk(net_hotdata.skbuff_cache,
+						GFP_ATOMIC | __GFP_NOWARN,
+						NAPI_SKB_CACHE_BULK,
+						nc->skb_cache);
 		if (unlikely(!nc->skb_count)) {
 			local_unlock_nested_bh(&napi_alloc_cache.bh_lock);
 			return NULL;
@@ -530,7 +531,7 @@ static struct sk_buff *__napi_build_skb(void *data, unsigned int frag_size)
 {
 	struct sk_buff *skb;
 
-	skb = napi_skb_cache_get();
+	skb = napi_skb_cache_get(true);
 	if (unlikely(!skb))
 		return NULL;
 
@@ -659,7 +660,7 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
 	/* Get the HEAD */
 	if ((flags & (SKB_ALLOC_FCLONE | SKB_ALLOC_NAPI)) == SKB_ALLOC_NAPI &&
 	    likely(node == NUMA_NO_NODE || node == numa_mem_id()))
-		skb = napi_skb_cache_get();
+		skb = napi_skb_cache_get(true);
 	else
 		skb = kmem_cache_alloc_node(cache, gfp_mask & ~GFP_DMA, node);
 	if (unlikely(!skb))
-- 
2.52.0.rc1.455.g30608eb744-goog