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Commit 0e9796b4 authored by Jarno Rajahalme's avatar Jarno Rajahalme Committed by Pravin B Shelar
Browse files

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: default avatarJarno Rajahalme <jrajahalme@nicira.com>
Signed-off-by: default avatarPravin B Shelar <pshelar@nicira.com>
parent 86ec8dba

net/openvswitch/datapath.c

+29 −25
Original line number Diff line number Diff line
@@ -663,7 +663,7 @@ static size_t ovs_flow_cmd_msg_size(const struct sw_flow_actions *acts) 
}



/* Called with ovs_mutex or RCU read lock. */

static int ovs_flow_cmd_fill_info(struct sw_flow *flow, struct datapath *dp,

static int ovs_flow_cmd_fill_info(const struct sw_flow *flow, int dp_ifindex,

				  struct sk_buff *skb, u32 portid,

				  u32 seq, u32 flags, u8 cmd)

{
@@ -680,7 +680,7 @@ static int ovs_flow_cmd_fill_info(struct sw_flow *flow, struct datapath *dp, 
	if (!ovs_header)

		return -EMSGSIZE;



	ovs_header->dp_ifindex = get_dpifindex(dp);

	ovs_header->dp_ifindex = dp_ifindex;



	/* Fill flow key. */

	nla = nla_nest_start(skb, OVS_FLOW_ATTR_KEY);
@@ -703,6 +703,7 @@ static int ovs_flow_cmd_fill_info(struct sw_flow *flow, struct datapath *dp, 
	nla_nest_end(skb, nla);



	ovs_flow_stats_get(flow, &stats, &used, &tcp_flags);



	if (used &&

	    nla_put_u64(skb, OVS_FLOW_ATTR_USED, ovs_flow_used_time(used)))

		goto nla_put_failure;
@@ -730,9 +731,9 @@ static int ovs_flow_cmd_fill_info(struct sw_flow *flow, struct datapath *dp, 
		const struct sw_flow_actions *sf_acts;



		sf_acts = rcu_dereference_ovsl(flow->sf_acts);



		err = ovs_nla_put_actions(sf_acts->actions,

					  sf_acts->actions_len, skb);



		if (!err)

			nla_nest_end(skb, start);

		else {
@@ -753,41 +754,40 @@ error: 
	return err;

}



/* Must be called with ovs_mutex. */

static struct sk_buff *ovs_flow_cmd_alloc_info(struct sw_flow *flow,

/* May not be called with RCU read lock. */

static struct sk_buff *ovs_flow_cmd_alloc_info(const struct sw_flow_actions *acts,

					       struct genl_info *info,

					       bool always)

{

	struct sk_buff *skb;

	size_t len;



	if (!always && !ovs_must_notify(info, &ovs_dp_flow_multicast_group))

		return NULL;



	len = ovs_flow_cmd_msg_size(ovsl_dereference(flow->sf_acts));



	skb = genlmsg_new_unicast(len, info, GFP_KERNEL);

	skb = genlmsg_new_unicast(ovs_flow_cmd_msg_size(acts), info, GFP_KERNEL);

	if (!skb)

		return ERR_PTR(-ENOMEM);



	return skb;

}



/* Must be called with ovs_mutex. */

static struct sk_buff *ovs_flow_cmd_build_info(struct sw_flow *flow,

					       struct datapath *dp,

					       struct genl_info *info,

					       u8 cmd, bool always)

/* Called with ovs_mutex. */

static struct sk_buff *ovs_flow_cmd_build_info(const struct sw_flow *flow,

					       int dp_ifindex,

					       struct genl_info *info, u8 cmd,

					       bool always)

{

	struct sk_buff *skb;

	int retval;



	skb = ovs_flow_cmd_alloc_info(flow, info, always);

	skb = ovs_flow_cmd_alloc_info(ovsl_dereference(flow->sf_acts), info,

				      always);

	if (!skb || IS_ERR(skb))

		return skb;



	retval = ovs_flow_cmd_fill_info(flow, dp, skb, info->snd_portid,

					info->snd_seq, 0, cmd);

	retval = ovs_flow_cmd_fill_info(flow, dp_ifindex, skb,

					info->snd_portid, info->snd_seq, 0,

					cmd);

	BUG_ON(retval < 0);

	return skb;

}
@@ -868,8 +868,8 @@ static int ovs_flow_cmd_new_or_set(struct sk_buff *skb, struct genl_info *info) 
			goto err_flow_free;

		}



		reply = ovs_flow_cmd_build_info(flow, dp, info,

						OVS_FLOW_CMD_NEW, false);

		reply = ovs_flow_cmd_build_info(flow, ovs_header->dp_ifindex,

						info, OVS_FLOW_CMD_NEW, false);

	} else {

		/* We found a matching flow. */

		/* Bail out if we're not allowed to modify an existing flow.
@@ -895,8 +895,9 @@ static int ovs_flow_cmd_new_or_set(struct sk_buff *skb, struct genl_info *info) 
			rcu_assign_pointer(flow->sf_acts, acts);

			ovs_nla_free_flow_actions(old_acts);

		}

		reply = ovs_flow_cmd_build_info(flow, dp, info,

						OVS_FLOW_CMD_NEW, false);



		reply = ovs_flow_cmd_build_info(flow, ovs_header->dp_ifindex,

						info, OVS_FLOW_CMD_NEW, false);



		/* Clear stats. */

		if (a[OVS_FLOW_ATTR_CLEAR])
@@ -958,7 +959,8 @@ static int ovs_flow_cmd_get(struct sk_buff *skb, struct genl_info *info) 
		goto unlock;

	}



	reply = ovs_flow_cmd_build_info(flow, dp, info, OVS_FLOW_CMD_NEW, true);

	reply = ovs_flow_cmd_build_info(flow, ovs_header->dp_ifindex, info,

					OVS_FLOW_CMD_NEW, true);

	if (IS_ERR(reply)) {

		err = PTR_ERR(reply);

		goto unlock;
@@ -1005,7 +1007,8 @@ static int ovs_flow_cmd_del(struct sk_buff *skb, struct genl_info *info) 
		goto unlock;

	}



	reply = ovs_flow_cmd_alloc_info(flow, info, false);

	reply = ovs_flow_cmd_alloc_info(ovsl_dereference(flow->sf_acts), info,

					false);

	if (IS_ERR(reply)) {

		err = PTR_ERR(reply);

		goto unlock;
@@ -1014,7 +1017,8 @@ static int ovs_flow_cmd_del(struct sk_buff *skb, struct genl_info *info) 
	ovs_flow_tbl_remove(&dp->table, flow);



	if (reply) {

		err = ovs_flow_cmd_fill_info(flow, dp, reply, info->snd_portid,

		err = ovs_flow_cmd_fill_info(flow, ovs_header->dp_ifindex,

					     reply, info->snd_portid,

					     info->snd_seq, 0,

					     OVS_FLOW_CMD_DEL);

		BUG_ON(err < 0);
@@ -1054,7 +1058,7 @@ static int ovs_flow_cmd_dump(struct sk_buff *skb, struct netlink_callback *cb) 
		if (!flow)

			break;



		if (ovs_flow_cmd_fill_info(flow, dp, skb,

		if (ovs_flow_cmd_fill_info(flow, ovs_header->dp_ifindex, skb,

					   NETLINK_CB(cb->skb).portid,

					   cb->nlh->nlmsg_seq, NLM_F_MULTI,

					   OVS_FLOW_CMD_NEW) < 0)