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Commit bad43ca8 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

net: introduce skb_try_coalesce() 



Move tcp_try_coalesce() protocol independent part to
skb_try_coalesce().

skb_try_coalesce() can be used in IPv4 defrag and IPv6 reassembly,
to build optimized skbs (less sk_buff, and possibly less 'headers')

skb_try_coalesce() is zero copy, unless the copy can fit in destination
header (its a rare case)

kfree_skb_partial() is also moved to net/core/skbuff.c and exported,
because IPv6 will need it in patch (ipv6: use skb coalescing in
reassembly).

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Cc: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 3dde2598

include/linux/skbuff.h

+5 −0
Original line number Diff line number Diff line
@@ -562,6 +562,11 @@ extern void kfree_skb(struct sk_buff *skb); 
extern void consume_skb(struct sk_buff *skb);

extern void	       __kfree_skb(struct sk_buff *skb);

extern struct kmem_cache *skbuff_head_cache;



extern void kfree_skb_partial(struct sk_buff *skb, bool head_stolen);

extern bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from,

			     bool *fragstolen, int *delta_truesize);



extern struct sk_buff *__alloc_skb(unsigned int size,

				   gfp_t priority, int fclone, int node);

extern struct sk_buff *build_skb(void *data, unsigned int frag_size);

net/core/skbuff.c

+86 −0
Original line number Diff line number Diff line
@@ -3346,3 +3346,89 @@ void __skb_warn_lro_forwarding(const struct sk_buff *skb) 
			     skb->dev->name);

}

EXPORT_SYMBOL(__skb_warn_lro_forwarding);



void kfree_skb_partial(struct sk_buff *skb, bool head_stolen)

{

	if (head_stolen)

		kmem_cache_free(skbuff_head_cache, skb);

	else

		__kfree_skb(skb);

}

EXPORT_SYMBOL(kfree_skb_partial);



/**

 * skb_try_coalesce - try to merge skb to prior one

 * @to: prior buffer

 * @from: buffer to add

 * @fragstolen: pointer to boolean

 *

 */

bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from,

		      bool *fragstolen, int *delta_truesize)

{

	int i, delta, len = from->len;



	*fragstolen = false;



	if (skb_cloned(to))

		return false;



	if (len <= skb_tailroom(to)) {

		BUG_ON(skb_copy_bits(from, 0, skb_put(to, len), len));

		*delta_truesize = 0;

		return true;

	}



	if (skb_has_frag_list(to) || skb_has_frag_list(from))

		return false;



	if (skb_headlen(from) != 0) {

		struct page *page;

		unsigned int offset;



		if (skb_shinfo(to)->nr_frags +

		    skb_shinfo(from)->nr_frags >= MAX_SKB_FRAGS)

			return false;



		if (skb_head_is_locked(from))

			return false;



		delta = from->truesize - SKB_DATA_ALIGN(sizeof(struct sk_buff));



		page = virt_to_head_page(from->head);

		offset = from->data - (unsigned char *)page_address(page);



		skb_fill_page_desc(to, skb_shinfo(to)->nr_frags,

				   page, offset, skb_headlen(from));

		*fragstolen = true;

	} else {

		if (skb_shinfo(to)->nr_frags +

		    skb_shinfo(from)->nr_frags > MAX_SKB_FRAGS)

			return false;



		delta = from->truesize -

			SKB_TRUESIZE(skb_end_pointer(from) - from->head);

	}



	WARN_ON_ONCE(delta < len);



	memcpy(skb_shinfo(to)->frags + skb_shinfo(to)->nr_frags,

	       skb_shinfo(from)->frags,

	       skb_shinfo(from)->nr_frags * sizeof(skb_frag_t));

	skb_shinfo(to)->nr_frags += skb_shinfo(from)->nr_frags;



	if (!skb_cloned(from))

		skb_shinfo(from)->nr_frags = 0;



	/* if the skb is cloned this does nothing since we set nr_frags to 0 */

	for (i = 0; i < skb_shinfo(from)->nr_frags; i++)

		skb_frag_ref(from, i);



	to->truesize += delta;

	to->len += len;

	to->data_len += len;



	*delta_truesize = delta;

	return true;

}

EXPORT_SYMBOL(skb_try_coalesce);

net/ipv4/tcp_input.c

+3 −64
Original line number Diff line number Diff line
@@ -4549,84 +4549,23 @@ static bool tcp_try_coalesce(struct sock *sk, 
			     struct sk_buff *from,

			     bool *fragstolen)

{

	int i, delta, len = from->len;

	int delta;



	*fragstolen = false;



	if (tcp_hdr(from)->fin || skb_cloned(to))

	if (tcp_hdr(from)->fin)

		return false;



	if (len <= skb_tailroom(to)) {

		BUG_ON(skb_copy_bits(from, 0, skb_put(to, len), len));

		goto merge;

	}



	if (skb_has_frag_list(to) || skb_has_frag_list(from))

		return false;



	if (skb_headlen(from) != 0) {

		struct page *page;

		unsigned int offset;



		if (skb_shinfo(to)->nr_frags +

		    skb_shinfo(from)->nr_frags >= MAX_SKB_FRAGS)

			return false;



		if (skb_head_is_locked(from))

			return false;



		delta = from->truesize - SKB_DATA_ALIGN(sizeof(struct sk_buff));



		page = virt_to_head_page(from->head);

		offset = from->data - (unsigned char *)page_address(page);



		skb_fill_page_desc(to, skb_shinfo(to)->nr_frags,

				   page, offset, skb_headlen(from));

		*fragstolen = true;

	} else {

		if (skb_shinfo(to)->nr_frags +

		    skb_shinfo(from)->nr_frags > MAX_SKB_FRAGS)

	if (!skb_try_coalesce(to, from, fragstolen, &delta))

		return false;



		delta = from->truesize -

			SKB_TRUESIZE(skb_end_pointer(from) - from->head);

	}



	WARN_ON_ONCE(delta < len);



	memcpy(skb_shinfo(to)->frags + skb_shinfo(to)->nr_frags,

	       skb_shinfo(from)->frags,

	       skb_shinfo(from)->nr_frags * sizeof(skb_frag_t));

	skb_shinfo(to)->nr_frags += skb_shinfo(from)->nr_frags;



	if (!skb_cloned(from))

		skb_shinfo(from)->nr_frags = 0;



	/* if the skb is cloned this does nothing since we set nr_frags to 0 */

	for (i = 0; i < skb_shinfo(from)->nr_frags; i++)

		skb_frag_ref(from, i);



	to->truesize += delta;

	atomic_add(delta, &sk->sk_rmem_alloc);

	sk_mem_charge(sk, delta);

	to->len += len;

	to->data_len += len;



merge:

	NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRCVCOALESCE);

	TCP_SKB_CB(to)->end_seq = TCP_SKB_CB(from)->end_seq;

	TCP_SKB_CB(to)->ack_seq = TCP_SKB_CB(from)->ack_seq;

	return true;

}



static void kfree_skb_partial(struct sk_buff *skb, bool head_stolen)

{

	if (head_stolen)

		kmem_cache_free(skbuff_head_cache, skb);

	else

		__kfree_skb(skb);

}



static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb)

{

	struct tcp_sock *tp = tcp_sk(sk);