dpaa_eth,temp: Temporarily revert skb recycling removal

Partially reverting commit acb600def2110b1310466c0e485c0d26299898ae, in
that we leave the skb recycling functions around until we rebase our
code onto the new 3.8 kernel base.
1. We'll first move this capability back into our driver.
2. At a later stage, we'll remove this capability in this particular
form from the driver altogether, as we integrate the new net APIs.

Signed-off-by: Bogdan Hamciuc <bogdan.hamciuc@freescale.com>

2 files changed, 71 insertions, 0 deletions

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 320e976..e401875 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -602,6 +602,9 @@ static inline struct sk_buff *alloc_skb_fclone(unsigned int size,
 	return __alloc_skb(size, priority, SKB_ALLOC_FCLONE, NUMA_NO_NODE);
 }
 
+extern void skb_recycle(struct sk_buff *skb);
+extern bool skb_recycle_check(struct sk_buff *skb, int skb_size);
+
 extern struct sk_buff *skb_morph(struct sk_buff *dst, struct sk_buff *src);
 extern int skb_copy_ubufs(struct sk_buff *skb, gfp_t gfp_mask);
 extern struct sk_buff *skb_clone(struct sk_buff *skb,
@@ -2738,6 +2741,27 @@ static inline void skb_checksum_none_assert(const struct sk_buff *skb)
 
 bool skb_partial_csum_set(struct sk_buff *skb, u16 start, u16 off);
 
+static inline bool skb_is_recycleable(const struct sk_buff *skb, int skb_size)
+{
+	if (irqs_disabled())
+		return false;
+
+	if (skb_shinfo(skb)->tx_flags & SKBTX_DEV_ZEROCOPY)
+		return false;
+
+	if (skb_is_nonlinear(skb) || skb->fclone != SKB_FCLONE_UNAVAILABLE)
+		return false;
+
+	skb_size = SKB_DATA_ALIGN(skb_size + NET_SKB_PAD);
+	if (skb_end_offset(skb) < skb_size)
+		return false;
+
+	if (skb_shared(skb) || skb_cloned(skb))
+		return false;
+
+	return true;
+}
+
 /**
  * skb_head_is_locked - Determine if the skb->head is locked down
  * @skb: skb to check
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 32443eb..f4a73cb 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -675,6 +675,53 @@ void consume_skb(struct sk_buff *skb)
 }
 EXPORT_SYMBOL(consume_skb);
 
+/**
+ * 	skb_recycle - clean up an skb for reuse
+ * 	@skb: buffer
+ *
+ * 	Recycles the skb to be reused as a receive buffer. This
+ * 	function does any necessary reference count dropping, and
+ * 	cleans up the skbuff as if it just came from __alloc_skb().
+ */
+void skb_recycle(struct sk_buff *skb)
+{
+	struct skb_shared_info *shinfo;
+
+	skb_release_head_state(skb);
+
+	shinfo = skb_shinfo(skb);
+	memset(shinfo, 0, offsetof(struct skb_shared_info, dataref));
+	atomic_set(&shinfo->dataref, 1);
+
+	memset(skb, 0, offsetof(struct sk_buff, tail));
+	skb->data = skb->head + NET_SKB_PAD;
+	skb_reset_tail_pointer(skb);
+}
+EXPORT_SYMBOL(skb_recycle);
+
+/**
+ *	skb_recycle_check - check if skb can be reused for receive
+ *	@skb: buffer
+ *	@skb_size: minimum receive buffer size
+ *
+ *	Checks that the skb passed in is not shared or cloned, and
+ *	that it is linear and its head portion at least as large as
+ *	skb_size so that it can be recycled as a receive buffer.
+ *	If these conditions are met, this function does any necessary
+ *	reference count dropping and cleans up the skbuff as if it
+ *	just came from __alloc_skb().
+ */
+bool skb_recycle_check(struct sk_buff *skb, int skb_size)
+{
+	if (!skb_is_recycleable(skb, skb_size))
+		return false;
+
+	skb_recycle(skb);
+
+	return true;
+}
+EXPORT_SYMBOL(skb_recycle_check);
+
 static void __copy_skb_header(struct sk_buff *new, const struct sk_buff *old)
 {
 	new->tstamp		= old->tstamp;