Commit 79eb15da authored by Eric Dumazet's avatar Eric Dumazet Committed by Jakub Kicinski
Browse files

ipv4: add net_hash_mix() dispersion to fib_info_laddrhash keys 



net/ipv4/fib_semantics.c uses a hash table (fib_info_laddrhash)
in which fib_sync_down_addr() can locate fib_info
based on IPv4 local address.

This hash table is resized based on total number of
hashed fib_info, but the hash function is only
using the local address.

For hosts having many active network namespaces,
all fib_info for loopback devices (IPv4 address 127.0.0.1)
are hashed into a single bucket, making netns dismantles
very slow.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reviewed-by: default avatarDavid Ahern <dsahern@kernel.org>
Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent d07418af

net/ipv4/fib_semantics.c

+15 −14
Original line number Diff line number Diff line
@@ -52,6 +52,7 @@ static DEFINE_SPINLOCK(fib_info_lock); 
static struct hlist_head *fib_info_hash;

static struct hlist_head *fib_info_laddrhash;

static unsigned int fib_info_hash_size;

static unsigned int fib_info_hash_bits;

static unsigned int fib_info_cnt;



#define DEVINDEX_HASHBITS 8
@@ -1247,13 +1248,13 @@ int fib_check_nh(struct net *net, struct fib_nh *nh, u32 table, u8 scope, 
	return err;

}



static inline unsigned int fib_laddr_hashfn(__be32 val)

static struct hlist_head *

fib_info_laddrhash_bucket(const struct net *net, __be32 val)

{

	unsigned int mask = (fib_info_hash_size - 1);

	u32 slot = hash_32(net_hash_mix(net) ^ (__force u32)val,

			   fib_info_hash_bits);



	return ((__force u32)val ^

		((__force u32)val >> 7) ^

		((__force u32)val >> 14)) & mask;

	return &fib_info_laddrhash[slot];

}



static struct hlist_head *fib_info_hash_alloc(int bytes)
@@ -1289,6 +1290,7 @@ static void fib_info_hash_move(struct hlist_head *new_info_hash, 
	old_info_hash = fib_info_hash;

	old_laddrhash = fib_info_laddrhash;

	fib_info_hash_size = new_size;

	fib_info_hash_bits = ilog2(new_size);



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

		struct hlist_head *head = &fib_info_hash[i];
@@ -1306,21 +1308,20 @@ static void fib_info_hash_move(struct hlist_head *new_info_hash, 
	}

	fib_info_hash = new_info_hash;



	fib_info_laddrhash = new_laddrhash;

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

		struct hlist_head *lhead = &fib_info_laddrhash[i];

		struct hlist_head *lhead = &old_laddrhash[i];

		struct hlist_node *n;

		struct fib_info *fi;



		hlist_for_each_entry_safe(fi, n, lhead, fib_lhash) {

			struct hlist_head *ldest;

			unsigned int new_hash;



			new_hash = fib_laddr_hashfn(fi->fib_prefsrc);

			ldest = &new_laddrhash[new_hash];

			ldest = fib_info_laddrhash_bucket(fi->fib_net,

							  fi->fib_prefsrc);

			hlist_add_head(&fi->fib_lhash, ldest);

		}

	}

	fib_info_laddrhash = new_laddrhash;



	spin_unlock_bh(&fib_info_lock);
@@ -1605,7 +1606,7 @@ struct fib_info *fib_create_info(struct fib_config *cfg, 
	if (fi->fib_prefsrc) {

		struct hlist_head *head;



		head = &fib_info_laddrhash[fib_laddr_hashfn(fi->fib_prefsrc)];

		head = fib_info_laddrhash_bucket(net, fi->fib_prefsrc);

		hlist_add_head(&fi->fib_lhash, head);

	}

	if (fi->nh) {
@@ -1877,16 +1878,16 @@ int fib_dump_info(struct sk_buff *skb, u32 portid, u32 seq, int event, 
 */

int fib_sync_down_addr(struct net_device *dev, __be32 local)

{

	int ret = 0;

	unsigned int hash = fib_laddr_hashfn(local);

	struct hlist_head *head = &fib_info_laddrhash[hash];

	int tb_id = l3mdev_fib_table(dev) ? : RT_TABLE_MAIN;

	struct net *net = dev_net(dev);

	struct hlist_head *head;

	struct fib_info *fi;

	int ret = 0;



	if (!fib_info_laddrhash || local == 0)

		return 0;



	head = fib_info_laddrhash_bucket(net, local);

	hlist_for_each_entry(fi, head, fib_lhash) {

		if (!net_eq(fi->fib_net, net) ||

		    fi->fib_tb_id != tb_id)