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_ring.
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Acked-by: NJesper Dangaard Brouer <brouer@redhat.com>
Tested-by: NJesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/linux/skb_array.h

+/*
+ *	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>
+#include <linux/if_vlan.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_len_with_tag(struct sk_buff *skb)
+{
+	if (likely(skb)) {
+		int len = skb->len;
+
+		if (skb_vlan_tag_present(skb))
+			len += VLAN_HLEN;
+
+		return len;
+	} else {
+		return 0;
+	}
+}
+
+static inline int skb_array_peek_len(struct skb_array *a)
+{
+	return PTR_RING_PEEK_CALL(&a->ring, __skb_array_len_with_tag);
+}
+
+static inline int skb_array_peek_len_irq(struct skb_array *a)
+{
+	return PTR_RING_PEEK_CALL_IRQ(&a->ring, __skb_array_len_with_tag);
+}
+
+static inline int skb_array_peek_len_bh(struct skb_array *a)
+{
+	return PTR_RING_PEEK_CALL_BH(&a->ring, __skb_array_len_with_tag);
+}
+
+static inline int skb_array_peek_len_any(struct skb_array *a)
+{
+	return PTR_RING_PEEK_CALL_ANY(&a->ring, __skb_array_len_with_tag);
+}
+
+static inline int skb_array_init(struct skb_array *a, int size, gfp_t gfp)
+{
+	return ptr_ring_init(&a->ring, size, gfp);
+}
+
+static inline void skb_array_cleanup(struct skb_array *a)
+{
+	ptr_ring_cleanup(&a->ring);
+}
+
+#endif /* _LINUX_SKB_ARRAY_H  */