From: Jesse Gross Date: Tue, 7 Jun 2011 02:17:25 +0000 (-0700) Subject: datapath: Simplify make_writable(). X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=10db8b20d2ed55417f625a3212db3b5cef0331d2;p=openvswitch datapath: Simplify make_writable(). The current implementation of make_writable() is both overly complex and unnecessarily aggressive about copying data. We can improve performance by only making a copy of the data if someone else holds a reference to the portion of the data that we want to modify. This means that if a clone is held by the TCP stack for retransmission then we do not need to make a copy if we are changing the IP header because it will get regenerated on retransmit anyways. Even when it is necessary to copy we avoid duplicating struct sk_buff. Signed-off-by: Jesse Gross Acked-by: Ben Pfaff --- diff --git a/datapath/actions.c b/datapath/actions.c index 319c783f..a8884a3d 100644 --- a/datapath/actions.c +++ b/datapath/actions.c @@ -31,44 +31,31 @@ static int do_execute_actions(struct datapath *, struct sk_buff *, struct sw_flow_actions *acts); -static struct sk_buff *make_writable(struct sk_buff *skb, unsigned min_headroom) +static int make_writable(struct sk_buff *skb, int write_len) { - if (skb_cloned(skb)) { - struct sk_buff *nskb; - unsigned headroom = max(min_headroom, skb_headroom(skb)); + if (!skb_cloned(skb) || skb_clone_writable(skb, write_len)) + return 0; - nskb = skb_copy_expand(skb, headroom, skb_tailroom(skb), GFP_ATOMIC); - if (nskb) { - set_skb_csum_bits(skb, nskb); - kfree_skb(skb); - return nskb; - } - } else { - unsigned int hdr_len = (skb_transport_offset(skb) - + sizeof(struct tcphdr)); - if (pskb_may_pull(skb, min(hdr_len, skb->len))) - return skb; - } - kfree_skb(skb); - return NULL; + return pskb_expand_head(skb, 0, 0, GFP_ATOMIC); } -static struct sk_buff *strip_vlan(struct sk_buff *skb) +static int strip_vlan(struct sk_buff *skb) { struct ethhdr *eh; + int err; if (vlan_tx_tag_present(skb)) { vlan_set_tci(skb, 0); - return skb; + return 0; } if (unlikely(skb->protocol != htons(ETH_P_8021Q) || skb->len < VLAN_ETH_HLEN)) - return skb; + return 0; - skb = make_writable(skb, 0); - if (unlikely(!skb)) - return NULL; + err = make_writable(skb, VLAN_ETH_HLEN); + if (unlikely(err)) + return err; if (get_ip_summed(skb) == OVS_CSUM_COMPLETE) skb->csum = csum_sub(skb->csum, csum_partial(skb->data @@ -81,21 +68,25 @@ static struct sk_buff *strip_vlan(struct sk_buff *skb) skb->protocol = eh->h_proto; skb->mac_header += VLAN_HLEN; - return skb; + return 0; } -static struct sk_buff *modify_vlan_tci(struct sk_buff *skb, __be16 tci) +static int modify_vlan_tci(struct sk_buff *skb, __be16 tci) { if (!vlan_tx_tag_present(skb) && skb->protocol == htons(ETH_P_8021Q)) { + int err; + if (unlikely(skb->len < VLAN_ETH_HLEN)) - return skb; + return 0; - skb = strip_vlan(skb); - if (unlikely(!skb)) - return NULL; + err = strip_vlan(skb); + if (unlikely(err)) + return err; } - return __vlan_hwaccel_put_tag(skb, ntohs(tci)); + __vlan_hwaccel_put_tag(skb, ntohs(tci)); + + return 0; } static bool is_ip(struct sk_buff *skb) @@ -118,19 +109,21 @@ static __sum16 *get_l4_checksum(struct sk_buff *skb) return NULL; } -static struct sk_buff *set_nw_addr(struct sk_buff *skb, const struct nlattr *a) +static int set_nw_addr(struct sk_buff *skb, const struct nlattr *a) { __be32 new_nwaddr = nla_get_be32(a); struct iphdr *nh; __sum16 *check; __be32 *nwaddr; + int err; if (unlikely(!is_ip(skb))) - return skb; + return 0; - skb = make_writable(skb, 0); - if (unlikely(!skb)) - return NULL; + err = make_writable(skb, skb_network_offset(skb) + + sizeof(struct iphdr)); + if (unlikely(err)) + return err; nh = ip_hdr(skb); nwaddr = nla_type(a) == ODP_ACTION_ATTR_SET_NW_SRC ? &nh->saddr : &nh->daddr; @@ -144,47 +137,52 @@ static struct sk_buff *set_nw_addr(struct sk_buff *skb, const struct nlattr *a) *nwaddr = new_nwaddr; - return skb; + return 0; } -static struct sk_buff *set_nw_tos(struct sk_buff *skb, u8 nw_tos) +static int set_nw_tos(struct sk_buff *skb, u8 nw_tos) { + struct iphdr *nh = ip_hdr(skb); + u8 old, new; + int err; + if (unlikely(!is_ip(skb))) - return skb; - - skb = make_writable(skb, 0); - if (skb) { - struct iphdr *nh = ip_hdr(skb); - u8 *f = &nh->tos; - u8 old = *f; - u8 new; - - /* Set the DSCP bits and preserve the ECN bits. */ - new = nw_tos | (nh->tos & INET_ECN_MASK); - csum_replace4(&nh->check, (__force __be32)old, - (__force __be32)new); - *f = new; - } - return skb; + return 0; + + err = make_writable(skb, skb_network_offset(skb) + + sizeof(struct iphdr)); + if (unlikely(err)) + return err; + + /* Set the DSCP bits and preserve the ECN bits. */ + old = nh->tos; + new = nw_tos | (nh->tos & INET_ECN_MASK); + csum_replace4(&nh->check, (__force __be32)old, + (__force __be32)new); + nh->tos = new; + + return 0; } -static struct sk_buff *set_tp_port(struct sk_buff *skb, const struct nlattr *a) +static int set_tp_port(struct sk_buff *skb, const struct nlattr *a) { struct udphdr *th; __sum16 *check; __be16 *port; + int err; if (unlikely(!is_ip(skb))) - return skb; + return 0; - skb = make_writable(skb, 0); - if (unlikely(!skb)) - return NULL; + err = make_writable(skb, skb_transport_offset(skb) + + sizeof(struct tcphdr)); + if (unlikely(err)) + return err; /* Must follow make_writable() since that can move the skb data. */ check = get_l4_checksum(skb); if (unlikely(!check)) - return skb; + return 0; /* * Update port and checksum. @@ -199,7 +197,7 @@ static struct sk_buff *set_tp_port(struct sk_buff *skb, const struct nlattr *a) *port = nla_get_be16(a); skb_clear_rxhash(skb); - return skb; + return 0; } static void do_output(struct datapath *dp, struct sk_buff *skb, int out_port) @@ -248,10 +246,12 @@ static int do_execute_actions(struct datapath *dp, struct sk_buff *skb, int prev_port = -1; u32 priority = skb->priority; const struct nlattr *a; - int rem, err; + int rem; for (a = acts->actions, rem = acts->actions_len; rem > 0; a = nla_next(a, &rem)) { + int err = 0; + if (prev_port != -1) { do_output(dp, skb_clone(skb, GFP_ATOMIC), prev_port); prev_port = -1; @@ -264,10 +264,6 @@ static int do_execute_actions(struct datapath *dp, struct sk_buff *skb, case ODP_ACTION_ATTR_CONTROLLER: err = output_control(dp, skb, nla_get_u64(a)); - if (err) { - kfree_skb(skb); - return err; - } break; case ODP_ACTION_ATTR_SET_TUNNEL: @@ -275,39 +271,37 @@ static int do_execute_actions(struct datapath *dp, struct sk_buff *skb, break; case ODP_ACTION_ATTR_SET_DL_TCI: - skb = modify_vlan_tci(skb, nla_get_be16(a)); + err = modify_vlan_tci(skb, nla_get_be16(a)); break; case ODP_ACTION_ATTR_STRIP_VLAN: - skb = strip_vlan(skb); + err = strip_vlan(skb); break; case ODP_ACTION_ATTR_SET_DL_SRC: - skb = make_writable(skb, 0); - if (!skb) - return -ENOMEM; - memcpy(eth_hdr(skb)->h_source, nla_data(a), ETH_ALEN); + err = make_writable(skb, ETH_HLEN); + if (likely(!err)) + memcpy(eth_hdr(skb)->h_source, nla_data(a), ETH_ALEN); break; case ODP_ACTION_ATTR_SET_DL_DST: - skb = make_writable(skb, 0); - if (!skb) - return -ENOMEM; - memcpy(eth_hdr(skb)->h_dest, nla_data(a), ETH_ALEN); + err = make_writable(skb, ETH_HLEN); + if (likely(!err)) + memcpy(eth_hdr(skb)->h_dest, nla_data(a), ETH_ALEN); break; case ODP_ACTION_ATTR_SET_NW_SRC: case ODP_ACTION_ATTR_SET_NW_DST: - skb = set_nw_addr(skb, a); + err = set_nw_addr(skb, a); break; case ODP_ACTION_ATTR_SET_NW_TOS: - skb = set_nw_tos(skb, nla_get_u8(a)); + err = set_nw_tos(skb, nla_get_u8(a)); break; case ODP_ACTION_ATTR_SET_TP_SRC: case ODP_ACTION_ATTR_SET_TP_DST: - skb = set_tp_port(skb, a); + err = set_tp_port(skb, a); break; case ODP_ACTION_ATTR_SET_PRIORITY: @@ -318,14 +312,18 @@ static int do_execute_actions(struct datapath *dp, struct sk_buff *skb, skb->priority = priority; break; } - if (!skb) - return -ENOMEM; + + if (unlikely(err)) { + kfree_skb(skb); + return err; + } } if (prev_port != -1) do_output(dp, skb, prev_port); else kfree_skb(skb); + return 0; }