ipv4: Restore old dst_free() behavior.
commit 404e0a8b6a55 (net: ipv4: fix RCU races on dst refcounts) tried
to solve a race but added a problem at device/fib dismantle time :
We really want to call dst_free() as soon as possible, even if sockets
still have dst in their cache.
dst_release() calls in free_fib_info_rcu() are not welcomed.
Root of the problem was that now we also cache output routes (in
nh_rth_output), we must use call_rcu() instead of call_rcu_bh() in
rt_free(), because output route lookups are done in process context.
Based on feedback and initial patch from David Miller (adding another
call_rcu_bh() call in fib, but it appears it was not the right fix)
I left the inet_sk_rx_dst_set() helper and added __rcu attributes
to nh_rth_output and nh_rth_input to better document what is going on in
this code.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/dst.h b/include/net/dst.h
index 31a9fd3..baf5978 100644
--- a/include/net/dst.h
+++ b/include/net/dst.h
@@ -61,7 +61,6 @@
#define DST_NOPEER 0x0040
#define DST_FAKE_RTABLE 0x0080
#define DST_XFRM_TUNNEL 0x0100
-#define DST_RCU_FREE 0x0200
unsigned short pending_confirm;
@@ -383,6 +382,12 @@
__dst_free(dst);
}
+static inline void dst_rcu_free(struct rcu_head *head)
+{
+ struct dst_entry *dst = container_of(head, struct dst_entry, rcu_head);
+ dst_free(dst);
+}
+
static inline void dst_confirm(struct dst_entry *dst)
{
dst->pending_confirm = 1;
diff --git a/include/net/inet_sock.h b/include/net/inet_sock.h
index e3fd34c..83b567f 100644
--- a/include/net/inet_sock.h
+++ b/include/net/inet_sock.h
@@ -253,13 +253,9 @@
{
struct dst_entry *dst = skb_dst(skb);
- if (atomic_inc_not_zero(&dst->__refcnt)) {
- if (!(dst->flags & DST_RCU_FREE))
- dst->flags |= DST_RCU_FREE;
-
- sk->sk_rx_dst = dst;
- inet_sk(sk)->rx_dst_ifindex = skb->skb_iif;
- }
+ dst_hold(dst);
+ sk->sk_rx_dst = dst;
+ inet_sk(sk)->rx_dst_ifindex = skb->skb_iif;
}
#endif /* _INET_SOCK_H */
diff --git a/include/net/ip_fib.h b/include/net/ip_fib.h
index e69c3a4..e521a03 100644
--- a/include/net/ip_fib.h
+++ b/include/net/ip_fib.h
@@ -81,8 +81,8 @@
__be32 nh_gw;
__be32 nh_saddr;
int nh_saddr_genid;
- struct rtable *nh_rth_output;
- struct rtable *nh_rth_input;
+ struct rtable __rcu *nh_rth_output;
+ struct rtable __rcu *nh_rth_input;
struct fnhe_hash_bucket *nh_exceptions;
};