From 58025e46ea2d39f1840d5b1be5edea3297cfd23f Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 5 Mar 2015 13:47:48 -0800 Subject: [PATCH] net: gro: remove obsolete code from skb_gro_receive() Some drivers use copybreak to copy tiny frames into smaller skb, and this smaller skb might not have skb->head_frag set for various reasons. skb_gro_receive() currently doesn't allow to aggregate the smaller skb into the previous GRO packet if this GRO packet has at least 2 MSS in it. Following workload easily demonstrates the problem. netperf -t TCP_RR -H target -- -r 3000,3000 (tcpdump shows one GRO packet with 2 MSS, plus one additional packet of 104 bytes that should have been appended.) It turns out that we can remove code from skb_gro_receive(), because commit 8a29111c7ca6 ("net: gro: allow to build full sized skb") and its followups removed the assumption that a GRO packet with a frag_list had to have an empty head. Removing this code allows the aggregation of the last (incomplete) frame in some RPC workloads. Note that tcp_gro_receive() already takes care of forcing a flush if necessary, including this case. If we want to avoid using frag_list in the first place (in forwarding workloads for example, as the outgoing NIC is generally not able to cope with skbs having a frag_list), we need to address this separately. Signed-off-by: Eric Dumazet Cc: Herbert Xu Signed-off-by: David S. Miller --- net/core/skbuff.c | 45 +-------------------------------------------- 1 file changed, 1 insertion(+), 44 deletions(-) diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 913b94a77060..47c32413d5b9 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -3206,10 +3206,9 @@ int skb_gro_receive(struct sk_buff **head, struct sk_buff *skb) struct skb_shared_info *pinfo, *skbinfo = skb_shinfo(skb); unsigned int offset = skb_gro_offset(skb); unsigned int headlen = skb_headlen(skb); - struct sk_buff *nskb, *lp, *p = *head; unsigned int len = skb_gro_len(skb); + struct sk_buff *lp, *p = *head; unsigned int delta_truesize; - unsigned int headroom; if (unlikely(p->len + len >= 65536)) return -E2BIG; @@ -3276,48 +3275,6 @@ int skb_gro_receive(struct sk_buff **head, struct sk_buff *skb) NAPI_GRO_CB(skb)->free = NAPI_GRO_FREE_STOLEN_HEAD; goto done; } - /* switch back to head shinfo */ - pinfo = skb_shinfo(p); - - if (pinfo->frag_list) - goto merge; - if (skb_gro_len(p) != pinfo->gso_size) - return -E2BIG; - - headroom = skb_headroom(p); - nskb = alloc_skb(headroom + skb_gro_offset(p), GFP_ATOMIC); - if (unlikely(!nskb)) - return -ENOMEM; - - __copy_skb_header(nskb, p); - nskb->mac_len = p->mac_len; - - skb_reserve(nskb, headroom); - __skb_put(nskb, skb_gro_offset(p)); - - skb_set_mac_header(nskb, skb_mac_header(p) - p->data); - skb_set_network_header(nskb, skb_network_offset(p)); - skb_set_transport_header(nskb, skb_transport_offset(p)); - - __skb_pull(p, skb_gro_offset(p)); - memcpy(skb_mac_header(nskb), skb_mac_header(p), - p->data - skb_mac_header(p)); - - skb_shinfo(nskb)->frag_list = p; - skb_shinfo(nskb)->gso_size = pinfo->gso_size; - pinfo->gso_size = 0; - __skb_header_release(p); - NAPI_GRO_CB(nskb)->last = p; - - nskb->data_len += p->len; - nskb->truesize += p->truesize; - nskb->len += p->len; - - *head = nskb; - nskb->next = p->next; - p->next = NULL; - - p = nskb; merge: delta_truesize = skb->truesize; -- 2.39.5