From 04a4bb55bcf35b63d40fd2725e58599ff8310dd7 Mon Sep 17 00:00:00 2001
From: Lennert Buytenhek <buytenh@marvell.com>
Date: Wed, 1 Oct 2008 02:33:12 -0700
Subject: [PATCH] net: add skb_recycle_check() to enable netdriver skb
recycling
This patch adds skb_recycle_check(), which can be used by a network
driver after transmitting an skb to check whether this skb can be
recycled as a receive buffer.
skb_recycle_check() checks that the skb is not shared or cloned, and
that it is linear and its head portion large enough (as determined by
the driver) to be recycled as a receive buffer. If these conditions
are met, it does any necessary reference count dropping and cleans
up the skbuff as if it just came from __alloc_skb().
Signed-off-by: Lennert Buytenhek <buytenh@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
include/linux/skbuff.h | 2 ++
net/core/skbuff.c | 41 +++++++++++++++++++++++++++++++++++++++--
2 files changed, 41 insertions(+), 2 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index a19ea43fea02..720b688c22b6 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -383,6 +383,8 @@ static inline struct sk_buff *alloc_skb_fclone(unsigned int size,
return __alloc_skb(size, priority, 1, -1);
}
+extern int 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 struct sk_buff *skb_clone(struct sk_buff *skb,
gfp_t priority);
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index ca1ccdf1ef76..2c218a0808b4 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -363,8 +363,7 @@ static void kfree_skbmem(struct sk_buff *skb)
}
}
-/* Free everything but the sk_buff shell. */
-static void skb_release_all(struct sk_buff *skb)
+static void skb_release_head_state(struct sk_buff *skb)
{
dst_release(skb->dst);
#ifdef CONFIG_XFRM
@@ -388,6 +387,12 @@ static void skb_release_all(struct sk_buff *skb)
skb->tc_verd = 0;
#endif
#endif
+}
+
+/* Free everything but the sk_buff shell. */
+static void skb_release_all(struct sk_buff *skb)
+{
+ skb_release_head_state(skb);
skb_release_data(skb);
}
@@ -424,6 +429,38 @@ void kfree_skb(struct sk_buff *skb)
__kfree_skb(skb);
}
+int skb_recycle_check(struct sk_buff *skb, int skb_size)
+{
+ struct skb_shared_info *shinfo;
+
+ if (skb_is_nonlinear(skb) || skb->fclone != SKB_FCLONE_UNAVAILABLE)
+ return 0;
+
+ skb_size = SKB_DATA_ALIGN(skb_size + NET_SKB_PAD);
+ if (skb_end_pointer(skb) - skb->head < skb_size)
+ return 0;
+
+ if (skb_shared(skb) || skb_cloned(skb))
+ return 0;
+
+ skb_release_head_state(skb);
+ shinfo = skb_shinfo(skb);
+ atomic_set(&shinfo->dataref, 1);
+ shinfo->nr_frags = 0;
+ shinfo->gso_size = 0;
+ shinfo->gso_segs = 0;
+ shinfo->gso_type = 0;
+ shinfo->ip6_frag_id = 0;
+ shinfo->frag_list = NULL;
+
+ memset(skb, 0, offsetof(struct sk_buff, tail));
+ skb_reset_tail_pointer(skb);
+ skb->data = skb->head + NET_SKB_PAD;
+
+ return 1;
+}
+EXPORT_SYMBOL(skb_recycle_check);
+
static void __copy_skb_header(struct sk_buff *new, const struct sk_buff *old)
{
new->tstamp = old->tstamp;
--
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