[PATCH] Avoid copying unfragmented udp NFS requests.

If an NFS request arrives in a linear skb,
we don't need to copy it, particularly if the
network card has already done the DUB checksum.

This patch only copies a request if it is
already non-linear.

diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index 6b455b1b13a9cb4242d09df7a07597e4a526a440..e03617f7aa085b2bcf00efc3416f77e9196fbc43 100644 (file)
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -564,16 +564,39 @@ svc_udp_recvfrom(struct svc_rqst *rqstp)
        set_bit(SK_DATA, &svsk->sk_flags); /* there may be more data... */
 
        len  = skb->len - sizeof(struct udphdr);
+       rqstp->rq_arg.len = len;
 
-       if (csum_partial_copy_to_xdr(&rqstp->rq_arg, skb)) {
-               /* checksum error */
-               skb_free_datagram(svsk->sk_sk, skb);
-               svc_sock_received(svsk);
-               return 0;
-       }
+       rqstp->rq_prot        = IPPROTO_UDP;
 
+       /* Get sender address */
+       rqstp->rq_addr.sin_family = AF_INET;
+       rqstp->rq_addr.sin_port = skb->h.uh->source;
+       rqstp->rq_addr.sin_addr.s_addr = skb->nh.iph->saddr;
+
+       if (skb_is_nonlinear(skb)) {
+               /* we have to copy */
+               if (csum_partial_copy_to_xdr(&rqstp->rq_arg, skb)) {
+                       /* checksum error */
+                       skb_free_datagram(svsk->sk_sk, skb);
+                       svc_sock_received(svsk);
+                       return 0;
+               }
+               skb_free_datagram(svsk->sk_sk, skb); 
+       } else {
+               /* we can use it in-place */
+               rqstp->rq_arg.head[0].iov_base = skb->data + sizeof(struct udphdr);
+               rqstp->rq_arg.head[0].iov_len = len;
+               if (skb->ip_summed != CHECKSUM_UNNECESSARY) {
+                       if ((unsigned short)csum_fold(skb_checksum(skb, 0, skb->len, skb->csum))) {
+                               skb_free_datagram(svsk->sk_sk, skb);
+                               svc_sock_received(svsk);
+                               return 0;
+                       }
+                       skb->ip_summed = CHECKSUM_UNNECESSARY;
+               }
+               rqstp->rq_skbuff = skb;
+       }
 
-       rqstp->rq_arg.len = len;
        rqstp->rq_arg.page_base = 0;
        if (len <= rqstp->rq_arg.head[0].iov_len) {
                rqstp->rq_arg.head[0].iov_len = len;
@@ -582,14 +605,6 @@ svc_udp_recvfrom(struct svc_rqst *rqstp)
                rqstp->rq_arg.page_len = len - rqstp->rq_arg.head[0].iov_len;
                rqstp->rq_argused += (rqstp->rq_arg.page_len + PAGE_SIZE - 1)/ PAGE_SIZE;
        }
-       rqstp->rq_prot        = IPPROTO_UDP;
-
-       /* Get sender address */
-       rqstp->rq_addr.sin_family = AF_INET;
-       rqstp->rq_addr.sin_port = skb->h.uh->source;
-       rqstp->rq_addr.sin_addr.s_addr = skb->nh.iph->saddr;
-
-       skb_free_datagram(svsk->sk_sk, skb);
 
        if (serv->sv_stats)
                serv->sv_stats->netudpcnt++;