cls_cgroup: Allow classifier cgroups to have their classid reset to 0

The network classifier cgroup initalizes each cgroups instance classid value to
0.  However, the sock_update_classid function only updates classid's in sockets
if the tasks cgroup classid is not zero, and if it differs from the current
classid.  The later check is to prevent cache line dirtying, but the former is
detrimental, as it prevents resetting a classid for a cgroup to 0.  While this
is not a common action, it has administrative usefulness (if the admin wants to
disable classification of a certain group temporarily for instance).

Easy fix, just remove the zero check.  Tested successfully by myself

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
CC: "David S. Miller" <davem@davemloft.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/sock.c b/net/core/sock.c
index 8f67ced8d6a808689255435dd412df132138af65..116786c55fe9a933f66cc54ece59cfae70538bb7 100644 (file)
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1230,7 +1230,7 @@ void sock_update_classid(struct sock *sk)
        rcu_read_lock();  /* doing current task, which cannot vanish. */
        classid = task_cls_classid(current);
        rcu_read_unlock();
-       if (classid && classid != sk->sk_classid)
+       if (classid != sk->sk_classid)
                sk->sk_classid = classid;
 }
 EXPORT_SYMBOL(sock_update_classid);