Re: Long stalls creating a new netns after a netns with a SMB client exits

On 7/31/17 4:01 PM, Cong Wang wrote:

quoted

quoted

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 3a19ea28339f..37db087b6c97 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c

@@ -1855,7 +1855,7 @@ void inet_sk_rx_dst_set(struct sock *sk, const

struct sk_buff *skb)
 {
        struct dst_entry *dst = skb_dst(skb);

-       if (dst && dst_hold_safe(dst)) {
+       if (0 && dst && dst_hold_safe(dst)) {
                sk->sk_rx_dst = dst;
                inet_sk(sk)->rx_dst_ifindex = skb->skb_iif;
        }

This removes the 200s stall (the test is IPv4/TCP based)

Interesting. This means we have a kernel socket which holds
the dst refcnt.

Right now there is no tracking that I am aware of for a dst cached on
the socket (outside of walking all sockets). I have been bitten by it
several times in trying to make various changes. It's basically a hidden
reference for the device.