udp: paged allocation with gso

When sending large datagrams that are later segmented, store data in
page frags to avoid copying from linear in skb_segment.

Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 25 insertions, 9 deletions

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index da4abbee10f7..f2338e40c37d 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -878,11 +878,13 @@ static int __ip_append_data(struct sock *sk,
         struct rtable *rt = (struct rtable *)cork->dst;
         unsigned int wmem_alloc_delta = 0;
         u32 tskey = 0;
+        bool paged;
 
         skb = skb_peek_tail(queue);
 
         exthdrlen = !skb ? rt->dst.header_len : 0;
         mtu = cork->gso_size ? IP_MAX_MTU : cork->fragsize;
+        paged = !!cork->gso_size;
 
         if (cork->tx_flags & SKBTX_ANY_SW_TSTAMP &&
             sk->sk_tsflags & SOF_TIMESTAMPING_OPT_ID)
@@ -934,6 +936,7 @@ static int __ip_append_data(struct sock *sk,
                         unsigned int fraglen;
                         unsigned int fraggap;
                         unsigned int alloclen;
+                        unsigned int pagedlen = 0;
                         struct sk_buff *skb_prev;
 alloc_new_skb:
                         skb_prev = skb;
@@ -954,8 +957,12 @@ alloc_new_skb:
                         if ((flags & MSG_MORE) &&
                             !(rt->dst.dev->features&NETIF_F_SG))
                                 alloclen = mtu;
-                        else
+                        else if (!paged)
                                 alloclen = fraglen;
+                        else {
+                                alloclen = min_t(int, fraglen, MAX_HEADER);
+                                pagedlen = fraglen - alloclen;
+                        }
 
                         alloclen += exthdrlen;
 
@@ -999,7 +1006,7 @@ alloc_new_skb:
                         /*
                          *      Find where to start putting bytes.
                          */
-                        data = skb_put(skb, fraglen + exthdrlen);
+                        data = skb_put(skb, fraglen + exthdrlen - pagedlen);
                         skb_set_network_header(skb, exthdrlen);
                         skb->transport_header = (skb->network_header +
                                                  fragheaderlen);
@@ -1015,7 +1022,7 @@ alloc_new_skb:
                                 pskb_trim_unique(skb_prev, maxfraglen);
                         }
 
-                        copy = datalen - transhdrlen - fraggap;
+                        copy = datalen - transhdrlen - fraggap - pagedlen;
                         if (copy > 0 && getfrag(from, data + transhdrlen, offset, copy, fraggap, skb) < 0) {
                                 err = -EFAULT;
                                 kfree_skb(skb);
@@ -1023,7 +1030,7 @@ alloc_new_skb:
                         }
 
                         offset += copy;
-                        length -= datalen - fraggap;
+                        length -= copy + transhdrlen;
                         transhdrlen = 0;
                         exthdrlen = 0;
                         csummode = CHECKSUM_NONE;
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index a1c4a78132d2..dfd8af41824e 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -1276,6 +1276,7 @@ static int __ip6_append_data(struct sock *sk,
         int csummode = CHECKSUM_NONE;
         unsigned int maxnonfragsize, headersize;
         unsigned int wmem_alloc_delta = 0;
+        bool paged;
 
         skb = skb_peek_tail(queue);
         if (!skb) {
@@ -1283,6 +1284,7 @@ static int __ip6_append_data(struct sock *sk,
                 dst_exthdrlen = rt->dst.header_len - rt->rt6i_nfheader_len;
         }
 
+        paged = !!cork->gso_size;
         mtu = cork->gso_size ? IP6_MAX_MTU : cork->fragsize;
         orig_mtu = mtu;
 
@@ -1374,6 +1376,7 @@ emsgsize:
                         unsigned int fraglen;
                         unsigned int fraggap;
                         unsigned int alloclen;
+                        unsigned int pagedlen = 0;
 alloc_new_skb:
                         /* There's no room in the current skb */
                         if (skb)
@@ -1396,11 +1399,17 @@ alloc_new_skb:
 
                         if (datalen > (cork->length <= mtu && !(cork->flags & IPCORK_ALLFRAG) ? mtu : maxfraglen) - fragheaderlen)
                                 datalen = maxfraglen - fragheaderlen - rt->dst.trailer_len;
+                        fraglen = datalen + fragheaderlen;
+
                         if ((flags & MSG_MORE) &&
                             !(rt->dst.dev->features&NETIF_F_SG))
                                 alloclen = mtu;
-                        else
-                                alloclen = datalen + fragheaderlen;
+                        else if (!paged)
+                                alloclen = fraglen;
+                        else {
+                                alloclen = min_t(int, fraglen, MAX_HEADER);
+                                pagedlen = fraglen - alloclen;
+                        }
 
                         alloclen += dst_exthdrlen;
 
@@ -1422,7 +1431,7 @@ alloc_new_skb:
                          */
                         alloclen += sizeof(struct frag_hdr);
 
-                        copy = datalen - transhdrlen - fraggap;
+                        copy = datalen - transhdrlen - fraggap - pagedlen;
                         if (copy < 0) {
                                 err = -EINVAL;
                                 goto error;
@@ -1461,7 +1470,7 @@ alloc_new_skb:
                         /*
                          *      Find where to start putting bytes
                          */
-                        data = skb_put(skb, fraglen);
+                        data = skb_put(skb, fraglen - pagedlen);
                         skb_set_network_header(skb, exthdrlen);
                         data += fragheaderlen;
                         skb->transport_header = (skb->network_header +
@@ -1484,7 +1493,7 @@ alloc_new_skb:
                         }
 
                         offset += copy;
-                        length -= datalen - fraggap;
+                        length -= copy + transhdrlen;
                         transhdrlen = 0;
                         exthdrlen = 0;
                         dst_exthdrlen = 0;