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inetpeer: restore small inet_peer structures 

Addition of rcu_head to struct inet_peer added 16bytes on 64bit arches.

Thats a bit unfortunate, since old size was exactly 64 bytes.

This can be solved, using an union between this rcu_head an four fields,
that are normally used only when a refcount is taken on inet_peer.
rcu_head is used only when refcnt=-1, right before structure freeing.

Add a inet_peer_refcheck() function to check this assertion for a while.

We can bring back SLAB_HWCACHE_ALIGN qualifier in kmem cache creation.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2010-06-16 04:52:13 +00:00 committed by David S. Miller
parent fdb93f8ac3
commit 317fe0e6c5
4 changed files with 36 additions and 11 deletions
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21
include/net/inetpeer.h
View File

@ -22,12 +22,22 @@ struct inet_peer {
__u32 dtime; /* the time of last use of not
* referenced entries */
atomic_t refcnt;
/*
* Once inet_peer is queued for deletion (refcnt == -1), following fields
* are not available: rid, ip_id_count, tcp_ts, tcp_ts_stamp
* We can share memory with rcu_head to keep inet_peer small
* (less then 64 bytes)
*/
union {
struct {
atomic_t rid; /* Frag reception counter */
atomic_t ip_id_count; /* IP ID for the next packet */
__u32 tcp_ts;
__u32 tcp_ts_stamp;
};
struct rcu_head rcu;
};
};
void inet_initpeers(void) __init;
@ -37,10 +47,21 @@ struct inet_peer *inet_getpeer(__be32 daddr, int create);
/* can be called from BH context or outside */
extern void inet_putpeer(struct inet_peer *p);
/*
* temporary check to make sure we dont access rid, ip_id_count, tcp_ts,
* tcp_ts_stamp if no refcount is taken on inet_peer
*/
static inline void inet_peer_refcheck(const struct inet_peer *p)
{
WARN_ON_ONCE(atomic_read(&p->refcnt) <= 0);
}
/* can be called with or without local BH being disabled */
static inline __u16 inet_getid(struct inet_peer *p, int more)
{
more++;
inet_peer_refcheck(p);
return atomic_add_return(more, &p->ip_id_count) - more;
}

4
net/ipv4/inetpeer.c
View File

@ -64,7 +64,7 @@
* usually under some other lock to prevent node disappearing
* dtime: unused node list lock
* v4daddr: unchangeable
* ip_id_count: idlock
* ip_id_count: atomic value (no lock needed)
*/
static struct kmem_cache *peer_cachep __read_mostly;
@ -129,7 +129,7 @@ void __init inet_initpeers(void)
peer_cachep = kmem_cache_create("inet_peer_cache",
sizeof(struct inet_peer),
0, SLAB_PANIC,
0, SLAB_HWCACHE_ALIGN | SLAB_PANIC,
NULL);
/* All the timers, started at system startup tend

1
net/ipv4/route.c
View File

@ -2881,6 +2881,7 @@ static int rt_fill_info(struct net *net,
error = rt->dst.error;
expires = rt->dst.expires ? rt->dst.expires - jiffies : 0;
if (rt->peer) {
inet_peer_refcheck(rt->peer);
id = atomic_read(&rt->peer->ip_id_count) & 0xffff;
if (rt->peer->tcp_ts_stamp) {
ts = rt->peer->tcp_ts;

7
net/ipv4/tcp_ipv4.c
View File

@ -204,12 +204,14 @@ int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
* TIME-WAIT * and initialize rx_opt.ts_recent from it,
* when trying new connection.
*/
if (peer != NULL &&
(u32)get_seconds() - peer->tcp_ts_stamp <= TCP_PAWS_MSL) {
if (peer) {
inet_peer_refcheck(peer);
if ((u32)get_seconds() - peer->tcp_ts_stamp <= TCP_PAWS_MSL) {
tp->rx_opt.ts_recent_stamp = peer->tcp_ts_stamp;
tp->rx_opt.ts_recent = peer->tcp_ts;
}
}
}
inet->inet_dport = usin->sin_port;
inet->inet_daddr = daddr;
@ -1351,6 +1353,7 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
(dst = inet_csk_route_req(sk, req)) != NULL &&
(peer = rt_get_peer((struct rtable *)dst)) != NULL &&
peer->v4daddr == saddr) {
inet_peer_refcheck(peer);
if ((u32)get_seconds() - peer->tcp_ts_stamp < TCP_PAWS_MSL &&
(s32)(peer->tcp_ts - req->ts_recent) >
TCP_PAWS_WINDOW) {