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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: Eric Dumazet <edumazet@google.com>
Cc: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2012-05-19 03:02:02 +00:00 committed by David S. Miller
parent 3dde259882
commit bad43ca832
3 changed files with 95 additions and 65 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
include/linux/skbuff.h
View File

@ -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);

86
net/core/skbuff.c
View File

@ -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);

69
net/ipv4/tcp_input.c
View File

@ -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 (!skb_try_coalesce(to, from, fragstolen, &delta))
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)
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);