net: core: introduce build_skb_around

The function build_skb() also have the responsibility to allocate and clear
the SKB structure. Introduce a new function build_skb_around(), that moves
the responsibility of allocation and clearing to the caller. This allows
caller to use kmem_cache (slab/slub) bulk allocation API.

Next patch use this function combined with kmem_cache_alloc_bulk.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Song Liu <songliubraving@fb.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index a06275a618f0c4573a92eba1db7d348868f6d8a6..e81f2b0e8a8396e72d38176fd790be5a6baf7fe6 100644 (file)
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1042,6 +1042,8 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t priority, int flags,
                            int node);
 struct sk_buff *__build_skb(void *data, unsigned int frag_size);
 struct sk_buff *build_skb(void *data, unsigned int frag_size);
+struct sk_buff *build_skb_around(struct sk_buff *skb,
+                                void *data, unsigned int frag_size);
 
 /**
  * alloc_skb - allocate a network buffer

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 9901f53228525efaa8049fccb33a8c1972505841..087622298d7718b4980ba624b02496b4dae777c6 100644 (file)
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -258,6 +258,33 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
 }
 EXPORT_SYMBOL(__alloc_skb);
 
+/* Caller must provide SKB that is memset cleared */
+static struct sk_buff *__build_skb_around(struct sk_buff *skb,
+                                         void *data, unsigned int frag_size)
+{
+       struct skb_shared_info *shinfo;
+       unsigned int size = frag_size ? : ksize(data);
+
+       size -= SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+
+       /* Assumes caller memset cleared SKB */
+       skb->truesize = SKB_TRUESIZE(size);
+       refcount_set(&skb->users, 1);
+       skb->head = data;
+       skb->data = data;
+       skb_reset_tail_pointer(skb);
+       skb->end = skb->tail + size;
+       skb->mac_header = (typeof(skb->mac_header))~0U;
+       skb->transport_header = (typeof(skb->transport_header))~0U;
+
+       /* make sure we initialize shinfo sequentially */
+       shinfo = skb_shinfo(skb);
+       memset(shinfo, 0, offsetof(struct skb_shared_info, dataref));
+       atomic_set(&shinfo->dataref, 1);
+
+       return skb;
+}
+
 /**
  * __build_skb - build a network buffer
  * @data: data buffer provided by caller
@@ -279,32 +306,15 @@ EXPORT_SYMBOL(__alloc_skb);
  */
 struct sk_buff *__build_skb(void *data, unsigned int frag_size)
 {
-       struct skb_shared_info *shinfo;
        struct sk_buff *skb;
-       unsigned int size = frag_size ? : ksize(data);
 
        skb = kmem_cache_alloc(skbuff_head_cache, GFP_ATOMIC);
-       if (!skb)
+       if (unlikely(!skb))
                return NULL;
 
-       size -= SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
-
        memset(skb, 0, offsetof(struct sk_buff, tail));
-       skb->truesize = SKB_TRUESIZE(size);
-       refcount_set(&skb->users, 1);
-       skb->head = data;
-       skb->data = data;
-       skb_reset_tail_pointer(skb);
-       skb->end = skb->tail + size;
-       skb->mac_header = (typeof(skb->mac_header))~0U;
-       skb->transport_header = (typeof(skb->transport_header))~0U;
 
-       /* make sure we initialize shinfo sequentially */
-       shinfo = skb_shinfo(skb);
-       memset(shinfo, 0, offsetof(struct skb_shared_info, dataref));
-       atomic_set(&shinfo->dataref, 1);
-
-       return skb;
+       return __build_skb_around(skb, data, frag_size);
 }
 
 /* build_skb() is wrapper over __build_skb(), that specifically
@@ -325,6 +335,29 @@ struct sk_buff *build_skb(void *data, unsigned int frag_size)
 }
 EXPORT_SYMBOL(build_skb);
 
+/**
+ * build_skb_around - build a network buffer around provided skb
+ * @skb: sk_buff provide by caller, must be memset cleared
+ * @data: data buffer provided by caller
+ * @frag_size: size of data, or 0 if head was kmalloced
+ */
+struct sk_buff *build_skb_around(struct sk_buff *skb,
+                                void *data, unsigned int frag_size)
+{
+       if (unlikely(!skb))
+               return NULL;
+
+       skb = __build_skb_around(skb, data, frag_size);
+
+       if (skb && frag_size) {
+               skb->head_frag = 1;
+               if (page_is_pfmemalloc(virt_to_head_page(data)))
+                       skb->pfmemalloc = 1;
+       }
+       return skb;
+}
+EXPORT_SYMBOL(build_skb_around);
+
 #define NAPI_SKB_CACHE_SIZE    64
 
 struct napi_alloc_cache {