diff mbox

[PATCHv5,net-next,1/6] skbuff: Introduce skb_to_sgvec_nomark to map skb without mark new end

Message ID 1390010068-15715-2-git-send-email-fan.du@windriver.com
State Awaiting Upstream, archived
Delegated to: David Miller
Headers show

Commit Message

fan.du Jan. 18, 2014, 1:54 a.m. UTC 
As compared with skb_to_sgvec, skb_to_sgvec_nomark only map skb to given sglist
without mark the sg which contain last skb data as the end. So the caller can
mannipulate sg list as will when padding new data after the first call without
calling sg_unmark_end to expend sg list.

Signed-off-by: Fan Du <fan.du@windriver.com>
---
 include/linux/skbuff.h |    2 ++
 net/core/skbuff.c      |   26 ++++++++++++++++++++++++++
 2 files changed, 28 insertions(+)
diff mbox

Patch

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 1f689e6..4fd28cc 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -691,6 +691,8 @@  struct sk_buff *skb_realloc_headroom(struct sk_buff *skb,
 				     unsigned int headroom);
 struct sk_buff *skb_copy_expand(const struct sk_buff *skb, int newheadroom,
 				int newtailroom, gfp_t priority);
+int skb_to_sgvec_nomark(struct sk_buff *skb, struct scatterlist *sg,
+			int offset, int len);
 int skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset,
 		 int len);
 int skb_cow_data(struct sk_buff *skb, int tailbits, struct sk_buff **trailer);
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 15057d2..19387c7 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3309,6 +3309,32 @@  __skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
 	return elt;
 }
 
+/* As compared with skb_to_sgvec, skb_to_sgvec_nomark only map skb to given
+ * sglist without mark the sg which contain last skb data as the end.
+ * So the caller can mannipulate sg list as will when padding new data after
+ * the first call without calling sg_unmark_end to expend sg list.
+ *
+ * Scenario to use skb_to_sgvec_nomark:
+ * 1. sg_init_table
+ * 2. skb_to_sgvec_nomark(payload1)
+ * 3. skb_to_sgvec_nomark(payload2)
+ *
+ * This is equivalent to:
+ * 1. sg_init_table
+ * 2. skb_to_sgvec(payload1)
+ * 3. sg_unmark_end
+ * 4. skb_to_sgvec(payload2)
+ *
+ * When mapping mutilple payload conditionally, skb_to_sgvec_nomark
+ * is more preferable.
+ */
+int skb_to_sgvec_nomark(struct sk_buff *skb, struct scatterlist *sg,
+			int offset, int len)
+{
+	return __skb_to_sgvec(skb, sg, offset, len);
+}
+EXPORT_SYMBOL_GPL(skb_to_sgvec_nomark);
+
 int skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)
 {
 	int nsg = __skb_to_sgvec(skb, sg, offset, len);