skbuff: Introduce skb_to_sgvec_nomark to map skb without mark new end (25a91d8d) · Commits · 戴 / test

include/linux/skbuff.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -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);

+26 −0

Original line number	Diff line number	Diff line
		@@ -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);