openvswitch: Reduce locking requirements.
Reduce and clarify locking requirements for ovs_flow_cmd_alloc_info(), ovs_flow_cmd_fill_info() and ovs_flow_cmd_build_info(). A datapath pointer is available only when holding a lock. Change ovs_flow_cmd_fill_info() and ovs_flow_cmd_build_info() to take a dp_ifindex directly, rather than a datapath pointer that is then (only) used to get the dp_ifindex. This is useful, since the dp_ifindex is available even when the datapath pointer is not, both before and after taking a lock, which makes further critical section reduction possible. Make ovs_flow_cmd_alloc_info() take an 'acts' argument instead a 'flow' pointer. This allows some future patches to do the allocation before acquiring the flow pointer. The locking requirements after this patch are: ovs_flow_cmd_alloc_info(): May be called without locking, must not be called while holding the RCU read lock (due to memory allocation). If 'acts' belong to a flow in the flow table, however, then the caller must hold ovs_mutex. ovs_flow_cmd_fill_info(): Either ovs_mutex or RCU read lock must be held. ovs_flow_cmd_build_info(): This calls both of the above, so the caller must hold ovs_mutex. Signed-off-by: Jarno Rajahalme <jrajahalme@nicira.com> Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
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@ -663,7 +663,7 @@ static size_t ovs_flow_cmd_msg_size(const struct sw_flow_actions *acts)
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}
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/* Called with ovs_mutex or RCU read lock. */
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static int ovs_flow_cmd_fill_info(struct sw_flow *flow, struct datapath *dp,
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static int ovs_flow_cmd_fill_info(const struct sw_flow *flow, int dp_ifindex,
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struct sk_buff *skb, u32 portid,
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u32 seq, u32 flags, u8 cmd)
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{
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@ -680,7 +680,7 @@ static int ovs_flow_cmd_fill_info(struct sw_flow *flow, struct datapath *dp,
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if (!ovs_header)
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return -EMSGSIZE;
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ovs_header->dp_ifindex = get_dpifindex(dp);
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ovs_header->dp_ifindex = dp_ifindex;
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/* Fill flow key. */
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nla = nla_nest_start(skb, OVS_FLOW_ATTR_KEY);
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@ -703,6 +703,7 @@ static int ovs_flow_cmd_fill_info(struct sw_flow *flow, struct datapath *dp,
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nla_nest_end(skb, nla);
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ovs_flow_stats_get(flow, &stats, &used, &tcp_flags);
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if (used &&
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nla_put_u64(skb, OVS_FLOW_ATTR_USED, ovs_flow_used_time(used)))
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goto nla_put_failure;
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@ -730,9 +731,9 @@ static int ovs_flow_cmd_fill_info(struct sw_flow *flow, struct datapath *dp,
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const struct sw_flow_actions *sf_acts;
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sf_acts = rcu_dereference_ovsl(flow->sf_acts);
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err = ovs_nla_put_actions(sf_acts->actions,
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sf_acts->actions_len, skb);
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if (!err)
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nla_nest_end(skb, start);
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else {
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@ -753,41 +754,40 @@ error:
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return err;
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}
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/* Must be called with ovs_mutex. */
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static struct sk_buff *ovs_flow_cmd_alloc_info(struct sw_flow *flow,
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/* May not be called with RCU read lock. */
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static struct sk_buff *ovs_flow_cmd_alloc_info(const struct sw_flow_actions *acts,
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struct genl_info *info,
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bool always)
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{
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struct sk_buff *skb;
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size_t len;
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if (!always && !ovs_must_notify(info, &ovs_dp_flow_multicast_group))
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return NULL;
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len = ovs_flow_cmd_msg_size(ovsl_dereference(flow->sf_acts));
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skb = genlmsg_new_unicast(len, info, GFP_KERNEL);
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skb = genlmsg_new_unicast(ovs_flow_cmd_msg_size(acts), info, GFP_KERNEL);
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if (!skb)
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return ERR_PTR(-ENOMEM);
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return skb;
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}
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/* Must be called with ovs_mutex. */
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static struct sk_buff *ovs_flow_cmd_build_info(struct sw_flow *flow,
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struct datapath *dp,
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struct genl_info *info,
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u8 cmd, bool always)
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/* Called with ovs_mutex. */
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static struct sk_buff *ovs_flow_cmd_build_info(const struct sw_flow *flow,
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int dp_ifindex,
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struct genl_info *info, u8 cmd,
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bool always)
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{
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struct sk_buff *skb;
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int retval;
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skb = ovs_flow_cmd_alloc_info(flow, info, always);
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skb = ovs_flow_cmd_alloc_info(ovsl_dereference(flow->sf_acts), info,
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always);
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if (!skb || IS_ERR(skb))
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return skb;
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retval = ovs_flow_cmd_fill_info(flow, dp, skb, info->snd_portid,
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info->snd_seq, 0, cmd);
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retval = ovs_flow_cmd_fill_info(flow, dp_ifindex, skb,
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info->snd_portid, info->snd_seq, 0,
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cmd);
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BUG_ON(retval < 0);
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return skb;
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}
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@ -868,8 +868,8 @@ static int ovs_flow_cmd_new_or_set(struct sk_buff *skb, struct genl_info *info)
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goto err_flow_free;
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}
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reply = ovs_flow_cmd_build_info(flow, dp, info,
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OVS_FLOW_CMD_NEW, false);
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reply = ovs_flow_cmd_build_info(flow, ovs_header->dp_ifindex,
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info, OVS_FLOW_CMD_NEW, false);
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} else {
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/* We found a matching flow. */
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/* Bail out if we're not allowed to modify an existing flow.
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@ -895,8 +895,9 @@ static int ovs_flow_cmd_new_or_set(struct sk_buff *skb, struct genl_info *info)
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rcu_assign_pointer(flow->sf_acts, acts);
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ovs_nla_free_flow_actions(old_acts);
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}
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reply = ovs_flow_cmd_build_info(flow, dp, info,
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OVS_FLOW_CMD_NEW, false);
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reply = ovs_flow_cmd_build_info(flow, ovs_header->dp_ifindex,
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info, OVS_FLOW_CMD_NEW, false);
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/* Clear stats. */
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if (a[OVS_FLOW_ATTR_CLEAR])
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@ -958,7 +959,8 @@ static int ovs_flow_cmd_get(struct sk_buff *skb, struct genl_info *info)
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goto unlock;
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}
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reply = ovs_flow_cmd_build_info(flow, dp, info, OVS_FLOW_CMD_NEW, true);
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reply = ovs_flow_cmd_build_info(flow, ovs_header->dp_ifindex, info,
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OVS_FLOW_CMD_NEW, true);
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if (IS_ERR(reply)) {
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err = PTR_ERR(reply);
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goto unlock;
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@ -1005,7 +1007,8 @@ static int ovs_flow_cmd_del(struct sk_buff *skb, struct genl_info *info)
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goto unlock;
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}
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reply = ovs_flow_cmd_alloc_info(flow, info, false);
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reply = ovs_flow_cmd_alloc_info(ovsl_dereference(flow->sf_acts), info,
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false);
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if (IS_ERR(reply)) {
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err = PTR_ERR(reply);
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goto unlock;
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@ -1014,7 +1017,8 @@ static int ovs_flow_cmd_del(struct sk_buff *skb, struct genl_info *info)
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ovs_flow_tbl_remove(&dp->table, flow);
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if (reply) {
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err = ovs_flow_cmd_fill_info(flow, dp, reply, info->snd_portid,
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err = ovs_flow_cmd_fill_info(flow, ovs_header->dp_ifindex,
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reply, info->snd_portid,
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info->snd_seq, 0,
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OVS_FLOW_CMD_DEL);
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BUG_ON(err < 0);
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@ -1054,7 +1058,7 @@ static int ovs_flow_cmd_dump(struct sk_buff *skb, struct netlink_callback *cb)
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if (!flow)
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break;
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if (ovs_flow_cmd_fill_info(flow, dp, skb,
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if (ovs_flow_cmd_fill_info(flow, ovs_header->dp_ifindex, skb,
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NETLINK_CB(cb->skb).portid,
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cb->nlh->nlmsg_seq, NLM_F_MULTI,
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OVS_FLOW_CMD_NEW) < 0)
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