net: avoid RCU for NOCACHE dst

[pandora-kernel.git] / net / core / dst.c

diff --git a/net/core/dst.c b/net/core/dst.c
index 32e542d..8abe628 100644 (file)
--- a/net/core/dst.c
+++ b/net/core/dst.c
@@ -271,13 +271,40 @@ void dst_release(struct dst_entry *dst)
        if (dst) {
                int newrefcnt;
 
-               smp_mb__before_atomic_dec();
                newrefcnt = atomic_dec_return(&dst->__refcnt);
                WARN_ON(newrefcnt < 0);
+               if (unlikely(dst->flags & DST_NOCACHE) && !newrefcnt) {
+                       dst = dst_destroy(dst);
+                       if (dst)
+                               __dst_free(dst);
+               }
        }
 }
 EXPORT_SYMBOL(dst_release);
 
+/**
+ * skb_dst_set_noref - sets skb dst, without a reference
+ * @skb: buffer
+ * @dst: dst entry
+ *
+ * Sets skb dst, assuming a reference was not taken on dst
+ * skb_dst_drop() should not dst_release() this dst
+ */
+void skb_dst_set_noref(struct sk_buff *skb, struct dst_entry *dst)
+{
+       WARN_ON(!rcu_read_lock_held() && !rcu_read_lock_bh_held());
+       /* If dst not in cache, we must take a reference, because
+        * dst_release() will destroy dst as soon as its refcount becomes zero
+        */
+       if (unlikely(dst->flags & DST_NOCACHE)) {
+               dst_hold(dst);
+               skb_dst_set(skb, dst);
+       } else {
+               skb->_skb_refdst = (unsigned long)dst | SKB_DST_NOREF;
+       }
+}
+EXPORT_SYMBOL(skb_dst_set_noref);
+
 /* Dirty hack. We did it in 2.2 (in __dst_free),
  * we have _very_ good reasons not to repeat
  * this mistake in 2.3, but we have no choice