Commit 169af346 authored by David S. Miller's avatar David S. Miller
Browse files

Merge branch 'netns-Optimise-netns-ID-lookups' 



Guillaume Nault says:

====================
netns: Optimise netns ID lookups

Netns ID lookups can be easily protected by RCU, rather than by holding
a spinlock.

Patch 1 prepares the code, patch 2 does the RCU conversion, and finally
patch 3 stops disabling BHs on updates (patch 2 makes that unnecessary).
====================

Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parents 62140036 8d7e5dee

net/core/net_namespace.c

+38 −55
Original line number Diff line number Diff line
@@ -211,16 +211,10 @@ static int net_eq_idr(int id, void *net, void *peer) 
	return 0;

}



/* Should be called with nsid_lock held. If a new id is assigned, the bool alloc

 * is set to true, thus the caller knows that the new id must be notified via

 * rtnl.

 */

static int __peernet2id_alloc(struct net *net, struct net *peer, bool *alloc)

/* Must be called from RCU-critical section or with nsid_lock held */

static int __peernet2id(const struct net *net, struct net *peer)

{

	int id = idr_for_each(&net->netns_ids, net_eq_idr, peer);

	bool alloc_it = *alloc;



	*alloc = false;



	/* Magic value for id 0. */

	if (id == NET_ID_ZERO)
@@ -228,23 +222,9 @@ static int __peernet2id_alloc(struct net *net, struct net *peer, bool *alloc) 
	if (id > 0)

		return id;



	if (alloc_it) {

		id = alloc_netid(net, peer, -1);

		*alloc = true;

		return id >= 0 ? id : NETNSA_NSID_NOT_ASSIGNED;

	}



	return NETNSA_NSID_NOT_ASSIGNED;

}



/* should be called with nsid_lock held */

static int __peernet2id(struct net *net, struct net *peer)

{

	bool no = false;



	return __peernet2id_alloc(net, peer, &no);

}



static void rtnl_net_notifyid(struct net *net, int cmd, int id, u32 portid,

			      struct nlmsghdr *nlh, gfp_t gfp);

/* This function returns the id of a peer netns. If no id is assigned, one will
@@ -252,26 +232,37 @@ static void rtnl_net_notifyid(struct net *net, int cmd, int id, u32 portid, 
 */

int peernet2id_alloc(struct net *net, struct net *peer, gfp_t gfp)

{

	bool alloc = false, alive = false;

	int id;



	if (refcount_read(&net->count) == 0)

		return NETNSA_NSID_NOT_ASSIGNED;

	spin_lock_bh(&net->nsid_lock);

	/*

	 * When peer is obtained from RCU lists, we may race with



	spin_lock(&net->nsid_lock);

	id = __peernet2id(net, peer);

	if (id >= 0) {

		spin_unlock(&net->nsid_lock);

		return id;

	}



	/* When peer is obtained from RCU lists, we may race with

	 * its cleanup. Check whether it's alive, and this guarantees

	 * we never hash a peer back to net->netns_ids, after it has

	 * just been idr_remove()'d from there in cleanup_net().

	 */

	if (maybe_get_net(peer))

		alive = alloc = true;

	id = __peernet2id_alloc(net, peer, &alloc);

	spin_unlock_bh(&net->nsid_lock);

	if (alloc && id >= 0)

		rtnl_net_notifyid(net, RTM_NEWNSID, id, 0, NULL, gfp);

	if (alive)

	if (!maybe_get_net(peer)) {

		spin_unlock(&net->nsid_lock);

		return NETNSA_NSID_NOT_ASSIGNED;

	}



	id = alloc_netid(net, peer, -1);

	spin_unlock(&net->nsid_lock);



	put_net(peer);

	if (id < 0)

		return NETNSA_NSID_NOT_ASSIGNED;



	rtnl_net_notifyid(net, RTM_NEWNSID, id, 0, NULL, gfp);



	return id;

}

EXPORT_SYMBOL_GPL(peernet2id_alloc);
@@ -281,9 +272,10 @@ int peernet2id(struct net *net, struct net *peer) 
{

	int id;



	spin_lock_bh(&net->nsid_lock);

	rcu_read_lock();

	id = __peernet2id(net, peer);

	spin_unlock_bh(&net->nsid_lock);

	rcu_read_unlock();



	return id;

}

EXPORT_SYMBOL(peernet2id);
@@ -528,20 +520,20 @@ static void unhash_nsid(struct net *net, struct net *last) 
	for_each_net(tmp) {

		int id;



		spin_lock_bh(&tmp->nsid_lock);

		spin_lock(&tmp->nsid_lock);

		id = __peernet2id(tmp, net);

		if (id >= 0)

			idr_remove(&tmp->netns_ids, id);

		spin_unlock_bh(&tmp->nsid_lock);

		spin_unlock(&tmp->nsid_lock);

		if (id >= 0)

			rtnl_net_notifyid(tmp, RTM_DELNSID, id, 0, NULL,

					  GFP_KERNEL);

		if (tmp == last)

			break;

	}

	spin_lock_bh(&net->nsid_lock);

	spin_lock(&net->nsid_lock);

	idr_destroy(&net->netns_ids);

	spin_unlock_bh(&net->nsid_lock);

	spin_unlock(&net->nsid_lock);

}



static LLIST_HEAD(cleanup_list);
@@ -754,9 +746,9 @@ static int rtnl_net_newid(struct sk_buff *skb, struct nlmsghdr *nlh, 
		return PTR_ERR(peer);

	}



	spin_lock_bh(&net->nsid_lock);

	spin_lock(&net->nsid_lock);

	if (__peernet2id(net, peer) >= 0) {

		spin_unlock_bh(&net->nsid_lock);

		spin_unlock(&net->nsid_lock);

		err = -EEXIST;

		NL_SET_BAD_ATTR(extack, nla);

		NL_SET_ERR_MSG(extack,
@@ -765,7 +757,7 @@ static int rtnl_net_newid(struct sk_buff *skb, struct nlmsghdr *nlh, 
	}



	err = alloc_netid(net, peer, nsid);

	spin_unlock_bh(&net->nsid_lock);

	spin_unlock(&net->nsid_lock);

	if (err >= 0) {

		rtnl_net_notifyid(net, RTM_NEWNSID, err, NETLINK_CB(skb).portid,

				  nlh, GFP_KERNEL);
@@ -950,6 +942,7 @@ struct rtnl_net_dump_cb { 
	int s_idx;

};



/* Runs in RCU-critical section. */

static int rtnl_net_dumpid_one(int id, void *peer, void *data)

{

	struct rtnl_net_dump_cb *net_cb = (struct rtnl_net_dump_cb *)data;
@@ -1034,19 +1027,9 @@ static int rtnl_net_dumpid(struct sk_buff *skb, struct netlink_callback *cb) 
			goto end;

	}



	spin_lock_bh(&net_cb.tgt_net->nsid_lock);

	if (net_cb.fillargs.add_ref &&

	    !net_eq(net_cb.ref_net, net_cb.tgt_net) &&

	    !spin_trylock_bh(&net_cb.ref_net->nsid_lock)) {

		spin_unlock_bh(&net_cb.tgt_net->nsid_lock);

		err = -EAGAIN;

		goto end;

	}

	rcu_read_lock();

	idr_for_each(&net_cb.tgt_net->netns_ids, rtnl_net_dumpid_one, &net_cb);

	if (net_cb.fillargs.add_ref &&

	    !net_eq(net_cb.ref_net, net_cb.tgt_net))

		spin_unlock_bh(&net_cb.ref_net->nsid_lock);

	spin_unlock_bh(&net_cb.tgt_net->nsid_lock);

	rcu_read_unlock();



	cb->args[0] = net_cb.idx;

end:

CRA Git | Maintained and supported by SUSTech CRA and CCSE