Commit 20d677d3 authored by Sebastian Andrzej Siewior's avatar Sebastian Andrzej Siewior Committed by Paolo Abeni
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net/sched: Use nested-BH locking for sch_frag_data_storage 



sch_frag_data_storage 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.

Add local_lock_t to the struct and use local_lock_nested_bh() for locking.
This change adds only lockdep coverage and does not alter the functional
behaviour for !PREEMPT_RT.

Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://patch.msgid.link/20250512092736.229935-12-bigeasy@linutronix.de


Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent 7fe70c06

net/sched/sch_frag.c

+9 −1
Original line number Diff line number Diff line
@@ -16,14 +16,18 @@ struct sch_frag_data { 
	unsigned int l2_len;

	u8 l2_data[VLAN_ETH_HLEN];

	int (*xmit)(struct sk_buff *skb);

	local_lock_t bh_lock;

};



static DEFINE_PER_CPU(struct sch_frag_data, sch_frag_data_storage);

static DEFINE_PER_CPU(struct sch_frag_data, sch_frag_data_storage) = {

	.bh_lock = INIT_LOCAL_LOCK(bh_lock),

};



static int sch_frag_xmit(struct net *net, struct sock *sk, struct sk_buff *skb)

{

	struct sch_frag_data *data = this_cpu_ptr(&sch_frag_data_storage);



	lockdep_assert_held(&data->bh_lock);

	if (skb_cow_head(skb, data->l2_len) < 0) {

		kfree_skb(skb);

		return -ENOMEM;
@@ -95,6 +99,7 @@ static int sch_fragment(struct net *net, struct sk_buff *skb, 
		struct rtable sch_frag_rt = { 0 };

		unsigned long orig_dst;



		local_lock_nested_bh(&sch_frag_data_storage.bh_lock);

		sch_frag_prepare_frag(skb, xmit);

		dst_init(&sch_frag_rt.dst, &sch_frag_dst_ops, NULL,

			 DST_OBSOLETE_NONE, DST_NOCOUNT);
@@ -105,11 +110,13 @@ static int sch_fragment(struct net *net, struct sk_buff *skb, 
		IPCB(skb)->frag_max_size = mru;



		ret = ip_do_fragment(net, skb->sk, skb, sch_frag_xmit);

		local_unlock_nested_bh(&sch_frag_data_storage.bh_lock);

		refdst_drop(orig_dst);

	} else if (skb_protocol(skb, true) == htons(ETH_P_IPV6)) {

		unsigned long orig_dst;

		struct rt6_info sch_frag_rt;



		local_lock_nested_bh(&sch_frag_data_storage.bh_lock);

		sch_frag_prepare_frag(skb, xmit);

		memset(&sch_frag_rt, 0, sizeof(sch_frag_rt));

		dst_init(&sch_frag_rt.dst, &sch_frag_dst_ops, NULL,
@@ -122,6 +129,7 @@ static int sch_fragment(struct net *net, struct sk_buff *skb, 


		ret = ipv6_stub->ipv6_fragment(net, skb->sk, skb,

					       sch_frag_xmit);

		local_unlock_nested_bh(&sch_frag_data_storage.bh_lock);

		refdst_drop(orig_dst);

	} else {

		net_warn_ratelimited("Fail frag %s: eth=%x, MRU=%d, MTU=%d\n",