Re: [PATCH v6 3/3] skb_array: array based FIFO for skbs

A simple array based FIFO of pointers.  Intended for net stack so uses
skbs for type safety. Implemented as a set of wrappers around ptr_array.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
  include/linux/skb_array.h | 129 ++++++++++++++++++++++++++++++++++++++++++++++
  1 file changed, 129 insertions(+)
  create mode 100644 include/linux/skb_array.h

diff --git a/include/linux/skb_array.h b/include/linux/skb_array.h
new file mode 100644
index 0000000..cb67076
--- /dev/null
+++ b/include/linux/skb_array.h

@@ -0,0 +1,129 @@
+/*
+ *	Definitions for the 'struct skb_array' datastructure.
+ *
+ *	Author:
+ *		Michael S. Tsirkin <mst@redhat.com>
+ *
+ *	Copyright (C) 2016 Red Hat, Inc.
+ *
+ *	This program is free software; you can redistribute it and/or modify it
+ *	under the terms of the GNU General Public License as published by the
+ *	Free Software Foundation; either version 2 of the License, or (at your
+ *	option) any later version.
+ *
+ *	Limited-size FIFO of skbs. Can be used more or less whenever
+ *	sk_buff_head can be used, except you need to know the queue size in
+ *	advance.
+ *	Implemented as a type-safe wrapper around ptr_ring.
+ */
+
+#ifndef _LINUX_SKB_ARRAY_H
+#define _LINUX_SKB_ARRAY_H 1
+
+#ifdef __KERNEL__
+#include <linux/ptr_ring.h>
+#include <linux/skbuff.h>
+#endif
+
+struct skb_array {
+	struct ptr_ring ring;
+};
+
+/* Might be slightly faster than skb_array_full below, but callers invoking
+ * this in a loop must use a compiler barrier, for example cpu_relax().
+ */
+static inline bool __skb_array_full(struct skb_array *a)
+{
+	return __ptr_ring_full(&a->ring);
+}
+
+static inline bool skb_array_full(struct skb_array *a)
+{
+	return ptr_ring_full(&a->ring);
+}
+
+static inline int skb_array_produce(struct skb_array *a, struct sk_buff *skb)
+{
+	return ptr_ring_produce(&a->ring, skb);
+}
+
+static inline int skb_array_produce_irq(struct skb_array *a, struct sk_buff *skb)
+{
+	return ptr_ring_produce_irq(&a->ring, skb);
+}
+
+static inline int skb_array_produce_bh(struct skb_array *a, struct sk_buff *skb)
+{
+	return ptr_ring_produce_bh(&a->ring, skb);
+}
+
+static inline int skb_array_produce_any(struct skb_array *a, struct sk_buff *skb)
+{
+	return ptr_ring_produce_any(&a->ring, skb);
+}
+
+/* Might be slightly faster than skb_array_empty below, but callers invoking
+ * this in a loop must take care to use a compiler barrier, for example
+ * cpu_relax().
+ */
+static inline bool __skb_array_empty(struct skb_array *a)
+{
+	return !__ptr_ring_peek(&a->ring);
+}
+
+static inline bool skb_array_empty(struct skb_array *a)
+{
+	return ptr_ring_empty(&a->ring);
+}
+
+static inline struct sk_buff *skb_array_consume(struct skb_array *a)
+{
+	return ptr_ring_consume(&a->ring);
+}
+
+static inline struct sk_buff *skb_array_consume_irq(struct skb_array *a)
+{
+	return ptr_ring_consume_irq(&a->ring);
+}
+
+static inline struct sk_buff *skb_array_consume_any(struct skb_array *a)
+{
+	return ptr_ring_consume_any(&a->ring);
+}
+
+static inline struct sk_buff *skb_array_consume_bh(struct skb_array *a)
+{
+	return ptr_ring_consume_bh(&a->ring);
+}
+
+static inline int skb_array_peek_len(struct skb_array *a)
+{
+	return PTR_RING_PEEK_FIELD(&a->ring, struct sk_buff, len, 0);
+}