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>

1 files changed, 3 insertions, 64 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index b961ef54b17d..cfa2aa128342 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -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))
+        if (!skb_try_coalesce(to, from, fragstolen, &delta))
                 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);