Commit b6e81138 authored by Kuniyuki Iwashima's avatar Kuniyuki Iwashima Committed by David S. Miller
Browse files

af_unix: Define a per-netns hash table. 

This commit adds a per netns hash table for AF_UNIX, which size is fixed
as UNIX_HASH_SIZE for now.

The first implementation defines a per-netns hash table as a single array
of lock and list:

	struct unix_hashbucket {
		spinlock_t		lock;
		struct hlist_head	head;
	};

	struct netns_unix {
		struct unix_hashbucket	*hash;
		...
	};

But, Eric pointed out memory cost that the structure has holes because of
sizeof(spinlock_t), which is 4 (or more if LOCKDEP is enabled). [0]  It
could be expensive on a host with thousands of netns and few AF_UNIX
sockets.  For this reason, a per-netns hash table uses two dense arrays.

	struct unix_table {
		spinlock_t		*locks;
		struct hlist_head	*buckets;
	};

	struct netns_unix {
		struct unix_table	table;
		...
	};

Note the length of the list has a significant impact rather than lock
contention, so having shared locks can be an option.  But, per-netns
locks and lists still perform better than the global locks and per-netns
lists. [1]

Also, this patch adds a change so that struct netns_unix disappears from
struct net if CONFIG_UNIX is disabled.

[0]: https://lore.kernel.org/netdev/CANn89iLVxO5aqx16azNU7p7Z-nz5NrnM5QTqOzueVxEnkVTxyg@mail.gmail.com/
[1]: https://lore.kernel.org/netdev/20220617175215.1769-1-kuniyu@amazon.com/



Signed-off-by: default avatarKuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent f302d180

include/net/net_namespace.h

+2 −0
Original line number Diff line number Diff line
@@ -120,7 +120,9 @@ struct net { 
	struct netns_core	core;

	struct netns_mib	mib;

	struct netns_packet	packet;

#if IS_ENABLED(CONFIG_UNIX)

	struct netns_unix	unx;

#endif

	struct netns_nexthop	nexthop;

	struct netns_ipv4	ipv4;

#if IS_ENABLED(CONFIG_IPV6)

include/net/netns/unix.h

+6 −0
Original line number Diff line number Diff line
@@ -5,8 +5,14 @@ 
#ifndef __NETNS_UNIX_H__

#define __NETNS_UNIX_H__



struct unix_table {

	spinlock_t		*locks;

	struct hlist_head	*buckets;

};



struct ctl_table_header;

struct netns_unix {

	struct unix_table	table;

	int			sysctl_max_dgram_qlen;

	struct ctl_table_header	*ctl;

};

net/unix/af_unix.c

+32 −6
Original line number Diff line number Diff line
@@ -3559,7 +3559,7 @@ static const struct net_proto_family unix_family_ops = { 


static int __net_init unix_net_init(struct net *net)

{

	int error = -ENOMEM;

	int i;



	net->unx.sysctl_max_dgram_qlen = 10;

	if (unix_sysctl_register(net))
@@ -3567,18 +3567,44 @@ static int __net_init unix_net_init(struct net *net) 


#ifdef CONFIG_PROC_FS

	if (!proc_create_net("unix", 0, net->proc_net, &unix_seq_ops,

			sizeof(struct seq_net_private))) {

		unix_sysctl_unregister(net);

		goto out;

			     sizeof(struct seq_net_private)))

		goto err_sysctl;

#endif



	net->unx.table.locks = kvmalloc_array(UNIX_HASH_SIZE,

					      sizeof(spinlock_t), GFP_KERNEL);

	if (!net->unx.table.locks)

		goto err_proc;



	net->unx.table.buckets = kvmalloc_array(UNIX_HASH_SIZE,

						sizeof(struct hlist_head),

						GFP_KERNEL);

	if (!net->unx.table.buckets)

		goto free_locks;



	for (i = 0; i < UNIX_HASH_SIZE; i++) {

		spin_lock_init(&net->unx.table.locks[i]);

		INIT_HLIST_HEAD(&net->unx.table.buckets[i]);

	}



	return 0;



free_locks:

	kvfree(net->unx.table.locks);

err_proc:

#ifdef CONFIG_PROC_FS

	remove_proc_entry("unix", net->proc_net);

err_sysctl:

#endif

	error = 0;

	unix_sysctl_unregister(net);

out:

	return error;

	return -ENOMEM;

}



static void __net_exit unix_net_exit(struct net *net)

{

	kvfree(net->unx.table.buckets);

	kvfree(net->unx.table.locks);

	unix_sysctl_unregister(net);

	remove_proc_entry("unix", net->proc_net);

}