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>
diff --git a/include/net/inetpeer.h b/include/net/inetpeer.h
index 6174047..417d0c8 100644
--- a/include/net/inetpeer.h
+++ b/include/net/inetpeer.h
@@ -22,11 +22,21 @@
__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 @@
/* 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;
}