net: introduce netdev_alloc_frag()

Fix two issues introduced in commit a1c7fff7e18f5
( net: netdev_alloc_skb() use build_skb() )

- Must be IRQ safe (non NAPI drivers can use it)
- Must not leak the frag if build_skb() fails to allocate sk_buff

This patch introduces netdev_alloc_frag() for drivers willing to
use build_skb() instead of __netdev_alloc_skb() variants.

Factorize code so that :
__dev_alloc_skb() is a wrapper around __netdev_alloc_skb(), and
dev_alloc_skb() a wrapper around netdev_alloc_skb()

Use __GFP_COLD flag.

Almost all network drivers now benefit from skb->head_frag
infrastructure.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index bb47314..fe37c21 100644 (file)
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1680,31 +1680,11 @@ static inline void __skb_queue_purge(struct sk_buff_head *list)
                kfree_skb(skb);
 }
 
-/**
- *     __dev_alloc_skb - allocate an skbuff for receiving
- *     @length: length to allocate
- *     @gfp_mask: get_free_pages mask, passed to alloc_skb
- *
- *     Allocate a new &sk_buff and assign it a usage count of one. The
- *     buffer has unspecified headroom built in. Users should allocate
- *     the headroom they think they need without accounting for the
- *     built in space. The built in space is used for optimisations.
- *
- *     %NULL is returned if there is no free memory.
- */
-static inline struct sk_buff *__dev_alloc_skb(unsigned int length,
-                                             gfp_t gfp_mask)
-{
-       struct sk_buff *skb = alloc_skb(length + NET_SKB_PAD, gfp_mask);
-       if (likely(skb))
-               skb_reserve(skb, NET_SKB_PAD);
-       return skb;
-}
-
-extern struct sk_buff *dev_alloc_skb(unsigned int length);
+extern void *netdev_alloc_frag(unsigned int fragsz);
 
 extern struct sk_buff *__netdev_alloc_skb(struct net_device *dev,
-               unsigned int length, gfp_t gfp_mask);
+                                         unsigned int length,
+                                         gfp_t gfp_mask);
 
 /**
  *     netdev_alloc_skb - allocate an skbuff for rx on a specific device
@@ -1720,11 +1700,25 @@ extern struct sk_buff *__netdev_alloc_skb(struct net_device *dev,
  *     allocates memory it can be called from an interrupt.
  */
 static inline struct sk_buff *netdev_alloc_skb(struct net_device *dev,
-               unsigned int length)
+                                              unsigned int length)
 {
        return __netdev_alloc_skb(dev, length, GFP_ATOMIC);
 }
 
+/* legacy helper around __netdev_alloc_skb() */
+static inline struct sk_buff *__dev_alloc_skb(unsigned int length,
+                                             gfp_t gfp_mask)
+{
+       return __netdev_alloc_skb(NULL, length, gfp_mask);
+}
+
+/* legacy helper around netdev_alloc_skb() */
+static inline struct sk_buff *dev_alloc_skb(unsigned int length)
+{
+       return netdev_alloc_skb(NULL, length);
+}
+
+
 static inline struct sk_buff *__netdev_alloc_skb_ip_align(struct net_device *dev,
                unsigned int length, gfp_t gfp)
 {

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 7645df1..7ceb673 100644 (file)
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -300,6 +300,40 @@ struct netdev_alloc_cache {
 static DEFINE_PER_CPU(struct netdev_alloc_cache, netdev_alloc_cache);
 
 /**
+ * netdev_alloc_frag - allocate a page fragment
+ * @fragsz: fragment size
+ *
+ * Allocates a frag from a page for receive buffer.
+ * Uses GFP_ATOMIC allocations.
+ */
+void *netdev_alloc_frag(unsigned int fragsz)
+{
+       struct netdev_alloc_cache *nc;
+       void *data = NULL;
+       unsigned long flags;
+
+       local_irq_save(flags);
+       nc = &__get_cpu_var(netdev_alloc_cache);
+       if (unlikely(!nc->page)) {
+refill:
+               nc->page = alloc_page(GFP_ATOMIC | __GFP_COLD);
+               nc->offset = 0;
+       }
+       if (likely(nc->page)) {
+               if (nc->offset + fragsz > PAGE_SIZE) {
+                       put_page(nc->page);
+                       goto refill;
+               }
+               data = page_address(nc->page) + nc->offset;
+               nc->offset += fragsz;
+               get_page(nc->page);
+       }
+       local_irq_restore(flags);
+       return data;
+}
+EXPORT_SYMBOL(netdev_alloc_frag);
+
+/**
  *     __netdev_alloc_skb - allocate an skbuff for rx on a specific device
  *     @dev: network device to receive on
  *     @length: length to allocate
@@ -313,32 +347,20 @@ static DEFINE_PER_CPU(struct netdev_alloc_cache, netdev_alloc_cache);
  *     %NULL is returned if there is no free memory.
  */
 struct sk_buff *__netdev_alloc_skb(struct net_device *dev,
-               unsigned int length, gfp_t gfp_mask)
+                                  unsigned int length, gfp_t gfp_mask)
 {
-       struct sk_buff *skb;
+       struct sk_buff *skb = NULL;
        unsigned int fragsz = SKB_DATA_ALIGN(length + NET_SKB_PAD) +
                              SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
 
        if (fragsz <= PAGE_SIZE && !(gfp_mask & __GFP_WAIT)) {
-               struct netdev_alloc_cache *nc;
-               void *data = NULL;
+               void *data = netdev_alloc_frag(fragsz);
 
-               nc = &get_cpu_var(netdev_alloc_cache);
-               if (!nc->page) {
-refill:                        nc->page = alloc_page(gfp_mask);
-                       nc->offset = 0;
-               }
-               if (likely(nc->page)) {
-                       if (nc->offset + fragsz > PAGE_SIZE) {
-                               put_page(nc->page);
-                               goto refill;
-                       }
-                       data = page_address(nc->page) + nc->offset;
-                       nc->offset += fragsz;
-                       get_page(nc->page);
+               if (likely(data)) {
+                       skb = build_skb(data, fragsz);
+                       if (unlikely(!skb))
+                               put_page(virt_to_head_page(data));
                }
-               put_cpu_var(netdev_alloc_cache);
-               skb = data ? build_skb(data, fragsz) : NULL;
        } else {
                skb = __alloc_skb(length + NET_SKB_PAD, gfp_mask, 0, NUMA_NO_NODE);
        }
@@ -360,28 +382,6 @@ void skb_add_rx_frag(struct sk_buff *skb, int i, struct page *page, int off,
 }
 EXPORT_SYMBOL(skb_add_rx_frag);
 
-/**
- *     dev_alloc_skb - allocate an skbuff for receiving
- *     @length: length to allocate
- *
- *     Allocate a new &sk_buff and assign it a usage count of one. The
- *     buffer has unspecified headroom built in. Users should allocate
- *     the headroom they think they need without accounting for the
- *     built in space. The built in space is used for optimisations.
- *
- *     %NULL is returned if there is no free memory. Although this function
- *     allocates memory it can be called from an interrupt.
- */
-struct sk_buff *dev_alloc_skb(unsigned int length)
-{
-       /*
-        * There is more code here than it seems:
-        * __dev_alloc_skb is an inline
-        */
-       return __dev_alloc_skb(length, GFP_ATOMIC);
-}
-EXPORT_SYMBOL(dev_alloc_skb);
-
 static void skb_drop_list(struct sk_buff **listp)
 {
        struct sk_buff *list = *listp;