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authorEric Dumazet <eric.dumazet@gmail.com>2010-06-16 04:52:13 +0000
committerDavid S. Miller <davem@davemloft.net>2010-06-16 11:55:39 -0700
commit317fe0e6c5dc9448bcef41a2e31fecfd3dba7f55 (patch)
treec2a042e1c8bb96b7fdeadf658309ead1b6e8dabc /include/net/inetpeer.h
parentfdb93f8ac39aa5902f3d264edd50dffcabfdd13b (diff)
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>
Diffstat (limited to 'include/net/inetpeer.h')
-rw-r--r--include/net/inetpeer.h31
1 files changed, 26 insertions, 5 deletions
diff --git a/include/net/inetpeer.h b/include/net/inetpeer.h
index 617404730422..417d0c894f29 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;
}