From 25a91d8d91911f84a03a039339b29537e7f1970d Mon Sep 17 00:00:00 2001 From: Fan Du Date: Sat, 18 Jan 2014 09:54:23 +0800 Subject: [PATCH] skbuff: Introduce skb_to_sgvec_nomark to map skb without mark new end 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 Signed-off-by: Steffen Klassert --- include/linux/skbuff.h | 2 ++ net/core/skbuff.c | 26 ++++++++++++++++++++++++++ 2 files changed, 28 insertions(+) diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index f589c9af8cbf..c574bf3bd6f6 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 5976ef0846bd..f28c37996aad 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -3281,6 +3281,32 @@ __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); -- 2.39.5