netdev - [PATCH net-next 1/4] net: add SKB_HEAD

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Date:   Thu,  2 Feb 2023 18:57:58 +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:     netdev@...r.kernel.org, eric.dumazet@...il.com,
        Alexander Duyck <alexanderduyck@...com>,
        Soheil Hassas Yeganeh <soheil@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 1/4] 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@...gle.com>
---
 include/linux/skbuff.h |  8 ++++++++
 net/core/skbuff.c      | 18 ++++++------------
 2 files changed, 14 insertions(+), 12 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 5ba12185f43e311e37c9045763c3ee0efc274f2a..f2141b7e3940cee060e8443dbaa147b843eb43a0 100644
--- a/include/linux/skbuff.h
+++ b/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))
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index bb79b4cb89db344d23609f93b2bcca5103f1e92d..b73de8fb0756c02cf9ba4b7e90854c9c17728463 100644
--- a/net/core/skbuff.c
+++ b/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;
@@ -1936,8 +1933,7 @@ 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)
@@ -6288,8 +6284,7 @@ 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)
@@ -6407,8 +6402,7 @@ 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)
-- 
2.39.1.456.gfc5497dd1b-goog