ipv4: use skb coalescing in defragmentation

ip_frag_reasm() can use skb_try_coalesce() to build optimized skb,
reducing memory used by them (truesize), and reducing number of cache
line misses and overhead for the consumer.

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, 20 insertions, 6 deletions

diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
index 695b27f44161..9dbd3dd6022d 100644
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -545,6 +545,7 @@ static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
         int len;
         int ihlen;
         int err;
+        int sum_truesize;
         u8 ecn;
 
         ipq_kill(qp);
@@ -611,19 +612,32 @@ static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
                 atomic_add(clone->truesize, &qp->q.net->mem);
         }
 
-        skb_shinfo(head)->frag_list = head->next;
         skb_push(head, head->data - skb_network_header(head));
 
-        for (fp=head->next; fp; fp = fp->next) {
-                head->data_len += fp->len;
-                head->len += fp->len;
+        sum_truesize = head->truesize;
+        for (fp = head->next; fp;) {
+                bool headstolen;
+                int delta;
+                struct sk_buff *next = fp->next;
+
+                sum_truesize += fp->truesize;
                 if (head->ip_summed != fp->ip_summed)
                         head->ip_summed = CHECKSUM_NONE;
                 else if (head->ip_summed == CHECKSUM_COMPLETE)
                         head->csum = csum_add(head->csum, fp->csum);
-                head->truesize += fp->truesize;
+
+                if (skb_try_coalesce(head, fp, &headstolen, &delta)) {
+                        kfree_skb_partial(fp, headstolen);
+                } else {
+                        if (!skb_shinfo(head)->frag_list)
+                                skb_shinfo(head)->frag_list = fp;
+                        head->data_len += fp->len;
+                        head->len += fp->len;
+                        head->truesize += fp->truesize;
+                }
+                fp = next;
         }
-        atomic_sub(head->truesize, &qp->q.net->mem);
+        atomic_sub(sum_truesize, &qp->q.net->mem);
 
         head->next = NULL;
         head->dev = dev;