[PATCH v2 net-next 1/3] skbuff: open-code __build_skb() inside __napi_alloc_skb()

[Alexander Lobakin <alobakin@pm.me>]

In preparation for skbuff_heads caching and reusing, open-code
__build_skb() inside __napi_alloc_skb() with factoring out
the skbbuff_head allocation itself.
Note that the return value of __build_skb_around() is not checked
since it never returns anything except the given skb.

Signed-off-by: Alexander Lobakin <alobakin@pm.me>
---
 net/core/skbuff.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 7626a33cce59..dc3300dc2ac4 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -485,6 +485,11 @@ struct sk_buff *__netdev_alloc_skb(struct net_device *dev, unsigned int len,
 }
 EXPORT_SYMBOL(__netdev_alloc_skb);
 
+static struct sk_buff *napi_skb_cache_get(struct napi_alloc_cache *nc)
+{
+	return kmem_cache_alloc(skbuff_head_cache, GFP_ATOMIC);
+}
+
 /**
  *	__napi_alloc_skb - allocate skbuff for rx in a specific NAPI instance
  *	@napi: napi instance this buffer was allocated for
@@ -525,12 +530,15 @@ struct sk_buff *__napi_alloc_skb(struct napi_struct *napi, unsigned int len,
 	if (unlikely(!data))
 		return NULL;
 
-	skb = __build_skb(data, len);
+	skb = napi_skb_cache_get(nc);
 	if (unlikely(!skb)) {
 		skb_free_frag(data);
 		return NULL;
 	}
 
+	memset(skb, 0, offsetof(struct sk_buff, tail));
+	__build_skb_around(skb, data, len);
+
 	if (nc->page.pfmemalloc)
 		skb->pfmemalloc = 1;
 	skb->head_frag = 1;
-- 
2.30.0