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>

3 files changed, 10 insertions, 6 deletions

diff --git a/net/ipv4/inetpeer.c b/net/ipv4/inetpeer.c
index 349249fad2db..9ffa24b9a804 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 a291edbbc97f..03430de46166 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 7f9515c0379f..2e41e6f92968 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) {