net: Embed hh_cache inside of struct neighbour.
Now that there is a one-to-one correspondance between neighbour
and hh_cache entries, we no longer need:
1) dynamic allocation
2) attachment to dst->hh
3) refcounting
Initialization of the hh_cache entry is indicated by hh_len
being non-zero, and such initialization is always done with
the neighbour's lock held as a writer.
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index f879bb5..77a399f 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -297,6 +297,7 @@
n->updated = n->used = now;
n->nud_state = NUD_NONE;
n->output = neigh_blackhole;
+ seqlock_init(&n->hh.hh_lock);
n->parms = neigh_parms_clone(&tbl->parms);
setup_timer(&n->timer, neigh_timer_handler, (unsigned long)n);
@@ -702,14 +703,11 @@
if (neigh_del_timer(neigh))
printk(KERN_WARNING "Impossible event.\n");
- hh = neigh->hh;
- if (hh) {
- neigh->hh = NULL;
-
+ hh = &neigh->hh;
+ if (hh->hh_len) {
write_seqlock_bh(&hh->hh_lock);
hh->hh_output = neigh_blackhole;
write_sequnlock_bh(&hh->hh_lock);
- hh_cache_put(hh);
}
skb_queue_purge(&neigh->arp_queue);
@@ -737,8 +735,8 @@
neigh->output = neigh->ops->output;
- hh = neigh->hh;
- if (hh)
+ hh = &neigh->hh;
+ if (hh->hh_len)
hh->hh_output = neigh->ops->output;
}
@@ -755,8 +753,8 @@
neigh->output = neigh->ops->connected_output;
- hh = neigh->hh;
- if (hh)
+ hh = &neigh->hh;
+ if (hh->hh_len)
hh->hh_output = neigh->ops->hh_output;
}
@@ -1017,7 +1015,7 @@
}
EXPORT_SYMBOL(__neigh_event_send);
-static void neigh_update_hhs(const struct neighbour *neigh)
+static void neigh_update_hhs(struct neighbour *neigh)
{
struct hh_cache *hh;
void (*update)(struct hh_cache*, const struct net_device*, const unsigned char *)
@@ -1027,8 +1025,8 @@
update = neigh->dev->header_ops->cache_update;
if (update) {
- hh = neigh->hh;
- if (hh) {
+ hh = &neigh->hh;
+ if (hh->hh_len) {
write_seqlock_bh(&hh->hh_lock);
update(hh, neigh->dev, neigh->ha);
write_sequnlock_bh(&hh->hh_lock);
@@ -1214,62 +1212,29 @@
}
EXPORT_SYMBOL(neigh_event_ns);
-static inline bool neigh_hh_lookup(struct neighbour *n, struct dst_entry *dst)
-{
- struct hh_cache *hh;
-
- smp_rmb(); /* paired with smp_wmb() in neigh_hh_init() */
- hh = n->hh;
- if (hh) {
- atomic_inc(&hh->hh_refcnt);
- if (unlikely(cmpxchg(&dst->hh, NULL, hh) != NULL))
- hh_cache_put(hh);
- return true;
- }
- return false;
-}
-
/* called with read_lock_bh(&n->lock); */
-static void neigh_hh_init(struct neighbour *n, struct dst_entry *dst,
- __be16 protocol)
+static void neigh_hh_init(struct neighbour *n, struct dst_entry *dst)
{
- struct hh_cache *hh;
struct net_device *dev = dst->dev;
-
- if (likely(neigh_hh_lookup(n, dst)))
- return;
-
- /* slow path */
- hh = kzalloc(sizeof(*hh), GFP_ATOMIC);
- if (!hh)
- return;
-
- seqlock_init(&hh->hh_lock);
- atomic_set(&hh->hh_refcnt, 2);
-
- if (dev->header_ops->cache(n, hh, protocol)) {
- kfree(hh);
- return;
- }
+ __be16 prot = dst->ops->protocol;
+ struct hh_cache *hh = &n->hh;
write_lock_bh(&n->lock);
- /* must check if another thread already did the insert */
- if (neigh_hh_lookup(n, dst)) {
- kfree(hh);
+ /* Only one thread can come in here and initialize the
+ * hh_cache entry.
+ */
+ if (hh->hh_len)
goto end;
- }
+
+ if (dev->header_ops->cache(n, hh, prot))
+ goto end;
if (n->nud_state & NUD_CONNECTED)
hh->hh_output = n->ops->hh_output;
else
hh->hh_output = n->ops->output;
- smp_wmb(); /* paired with smp_rmb() in neigh_hh_lookup() */
- n->hh = hh;
-
- if (unlikely(cmpxchg(&dst->hh, NULL, hh) != NULL))
- hh_cache_put(hh);
end:
write_unlock_bh(&n->lock);
}
@@ -1312,10 +1277,8 @@
struct net_device *dev = neigh->dev;
unsigned int seq;
- if (dev->header_ops->cache &&
- !dst->hh &&
- !(dst->flags & DST_NOCACHE))
- neigh_hh_init(neigh, dst, dst->ops->protocol);
+ if (dev->header_ops->cache && !neigh->hh.hh_len)
+ neigh_hh_init(neigh, dst);
do {
seq = read_seqbegin(&neigh->ha_lock);