net: add SKB_HEAD_ALIGN() helper

We have many places using this expression:

 SKB_DATA_ALIGN(sizeof(struct skb_shared_info))

Use of SKB_HEAD_ALIGN() will allow to clean them.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/linux/skbuff.h

@@ -255,6 +255,14 @@
 #define SKB_DATA_ALIGN(X)	ALIGN(X, SMP_CACHE_BYTES)
 #define SKB_WITH_OVERHEAD(X)	\
 	((X) - SKB_DATA_ALIGN(sizeof(struct skb_shared_info)))
+
+/* For X bytes available in skb->head, what is the minimal
+ * allocation needed, knowing struct skb_shared_info needs
+ * to be aligned.
+ */
+#define SKB_HEAD_ALIGN(X) (SKB_DATA_ALIGN(X) + \
+	SKB_DATA_ALIGN(sizeof(struct skb_shared_info)))
+
 #define SKB_MAX_ORDER(X, ORDER) \
 	SKB_WITH_OVERHEAD((PAGE_SIZE << (ORDER)) - (X))
 #define SKB_MAX_HEAD(X)		(SKB_MAX_ORDER((X), 0))

net/core/skbuff.c

@@ -558,8 +558,7 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
 	 * aligned memory blocks, unless SLUB/SLAB debug is enabled.
 	 * Both skb->head and skb_shared_info are cache line aligned.
 	 */
-	size = SKB_DATA_ALIGN(size);
-	size += SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+	size = SKB_HEAD_ALIGN(size);
 	osize = kmalloc_size_roundup(size);
 	data = kmalloc_reserve(osize, gfp_mask, node, &pfmemalloc);
 	if (unlikely(!data))
@@ -632,8 +631,7 @@ struct sk_buff *__netdev_alloc_skb(struct net_device *dev, unsigned int len,
 		goto skb_success;
 	}
 
-	len += SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
-	len = SKB_DATA_ALIGN(len);
+	len = SKB_HEAD_ALIGN(len);
 
 	if (sk_memalloc_socks())
 		gfp_mask |= __GFP_MEMALLOC;
@@ -732,8 +730,7 @@ struct sk_buff *__napi_alloc_skb(struct napi_struct *napi, unsigned int len,
 		data = page_frag_alloc_1k(&nc->page_small, gfp_mask);
 		pfmemalloc = NAPI_SMALL_PAGE_PFMEMALLOC(nc->page_small);
 	} else {
-		len += SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
-		len = SKB_DATA_ALIGN(len);
+		len = SKB_HEAD_ALIGN(len);
 
 		data = page_frag_alloc(&nc->page, len, gfp_mask);
 		pfmemalloc = nc->page.pfmemalloc;
@@ -1938,8 +1935,7 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail,
 	if (skb_pfmemalloc(skb))
 		gfp_mask |= __GFP_MEMALLOC;
 
-	size = SKB_DATA_ALIGN(size);
-	size += SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+	size = SKB_HEAD_ALIGN(size);
 	size = kmalloc_size_roundup(size);
 	data = kmalloc_reserve(size, gfp_mask, NUMA_NO_NODE, NULL);
 	if (!data)
@@ -6289,8 +6285,7 @@ static int pskb_carve_inside_header(struct sk_buff *skb, const u32 off,
 	if (skb_pfmemalloc(skb))
 		gfp_mask |= __GFP_MEMALLOC;
 
-	size = SKB_DATA_ALIGN(size);
-	size += SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+	size = SKB_HEAD_ALIGN(size);
 	size = kmalloc_size_roundup(size);
 	data = kmalloc_reserve(size, gfp_mask, NUMA_NO_NODE, NULL);
 	if (!data)
@@ -6408,8 +6403,7 @@ static int pskb_carve_inside_nonlinear(struct sk_buff *skb, const u32 off,
 	if (skb_pfmemalloc(skb))
 		gfp_mask |= __GFP_MEMALLOC;
 
-	size = SKB_DATA_ALIGN(size);
-	size += SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+	size = SKB_HEAD_ALIGN(size);
 	size = kmalloc_size_roundup(size);
 	data = kmalloc_reserve(size, gfp_mask, NUMA_NO_NODE, NULL);
 	if (!data)