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Date: Wed, 16 Jun 2010 16:52:13 +0200
From: Eric Dumazet <eric.dumazet@...il.com>
To: David Miller <davem@...emloft.net>
Cc: netdev <netdev@...r.kernel.org>
Subject: [PATCH net-next-2.6] 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@...il.com>
---
include/net/inetpeer.h | 31 ++++++++++++++++++++++++++-----
net/ipv4/inetpeer.c | 4 ++--
net/ipv4/route.c | 1 +
net/ipv4/tcp_ipv4.c | 11 +++++++----
4 files changed, 36 insertions(+), 11 deletions(-)
diff --git a/include/net/inetpeer.h b/include/net/inetpeer.h
index 6174047..51c06af 100644
--- a/include/net/inetpeer.h
+++ b/include/net/inetpeer.h
@@ -22,11 +22,21 @@ struct inet_peer {
__u32 dtime; /* the time of last use of not
* referenced entries */
atomic_t refcnt;
- 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;
+ /*
+ * 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;
}
diff --git a/net/ipv4/inetpeer.c b/net/ipv4/inetpeer.c
index 349249f..bb58aed 100644
--- a/net/ipv4/inetpeer.c
+++ b/net/ipv4/inetpeer.c
@@ -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
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index a291edb..03430de 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -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;
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 7f9515c..2e41e6f 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -204,10 +204,12 @@ 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) {
- tp->rx_opt.ts_recent_stamp = peer->tcp_ts_stamp;
- tp->rx_opt.ts_recent = peer->tcp_ts;
+ 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;
+ }
}
}
@@ -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) {
--
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