From mboxrd@z Thu Jan 1 00:00:00 1970 From: Fan Du Subject: [PATCHv4 net-next 1/6] skbuff: Introduce skb_to_sgvec_nomark to map skb without mark new end Date: Wed, 15 Jan 2014 15:13:10 +0800 Message-ID: <1389769995-350-2-git-send-email-fan.du@windriver.com> References: <1389769995-350-1-git-send-email-fan.du@windriver.com> Mime-Version: 1.0 Content-Type: text/plain Cc: , To: Return-path: Received: from mail1.windriver.com ([147.11.146.13]:50661 "EHLO mail1.windriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751396AbaAOHNI (ORCPT ); Wed, 15 Jan 2014 02:13:08 -0500 In-Reply-To: <1389769995-350-1-git-send-email-fan.du@windriver.com> Sender: netdev-owner@vger.kernel.org List-ID: 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 --- 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 d97f2d0..c2eb3c4 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 1d641e7..466c0ef 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -3308,6 +3308,32 @@ __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); -- 1.7.9.5