net/sched: act_mirred: Move the recursion counter struct netdev_xmit

mirred_nest_level is a per-CPU variable and relies on disabled BH for its
locking. Without per-CPU locking in local_bh_disable() on PREEMPT_RT
this data structure requires explicit locking.

Move mirred_nest_level to struct netdev_xmit as u8, provide wrappers.

Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://patch.msgid.link/20250512092736.229935-11-bigeasy@linutronix.de
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/include/linux/netdevice_xmit.h b/include/linux/netdevice_xmit.h
index 38325e070296850570c5e514f3f3ecfba5631260..848735b3a7c02d934bb037f89100eeecd1b5466e 100644 (file)
--- a/include/linux/netdevice_xmit.h
+++ b/include/linux/netdevice_xmit.h
@@ -8,6 +8,9 @@ struct netdev_xmit {
 #ifdef CONFIG_NET_EGRESS
        u8  skip_txqueue;
 #endif
+#if IS_ENABLED(CONFIG_NET_ACT_MIRRED)
+       u8 sched_mirred_nest;
+#endif
 };
 
 #endif

diff --git a/net/sched/act_mirred.c b/net/sched/act_mirred.c
index 5b38143659249e66718348e0ec4ed3c7bc21c13d..5f01f567c934d3669d9a3058cff861a8fe5f88b6 100644 (file)
--- a/net/sched/act_mirred.c
+++ b/net/sched/act_mirred.c
@@ -30,7 +30,29 @@ static LIST_HEAD(mirred_list);
 static DEFINE_SPINLOCK(mirred_list_lock);
 
 #define MIRRED_NEST_LIMIT    4
-static DEFINE_PER_CPU(unsigned int, mirred_nest_level);
+
+#ifndef CONFIG_PREEMPT_RT
+static u8 tcf_mirred_nest_level_inc_return(void)
+{
+       return __this_cpu_inc_return(softnet_data.xmit.sched_mirred_nest);
+}
+
+static void tcf_mirred_nest_level_dec(void)
+{
+       __this_cpu_dec(softnet_data.xmit.sched_mirred_nest);
+}
+
+#else
+static u8 tcf_mirred_nest_level_inc_return(void)
+{
+       return current->net_xmit.sched_mirred_nest++;
+}
+
+static void tcf_mirred_nest_level_dec(void)
+{
+       current->net_xmit.sched_mirred_nest--;
+}
+#endif
 
 static bool tcf_mirred_is_act_redirect(int action)
 {
@@ -423,7 +445,7 @@ TC_INDIRECT_SCOPE int tcf_mirred_act(struct sk_buff *skb,
        int m_eaction;
        u32 blockid;
 
-       nest_level = __this_cpu_inc_return(mirred_nest_level);
+       nest_level = tcf_mirred_nest_level_inc_return();
        if (unlikely(nest_level > MIRRED_NEST_LIMIT)) {
                net_warn_ratelimited("Packet exceeded mirred recursion limit on dev %s\n",
                                     netdev_name(skb->dev));
@@ -454,7 +476,7 @@ TC_INDIRECT_SCOPE int tcf_mirred_act(struct sk_buff *skb,
                                   retval);
 
 dec_nest_level:
-       __this_cpu_dec(mirred_nest_level);
+       tcf_mirred_nest_level_dec();
 
        return retval;
 }