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Message-ID: <20240415132054.3822230-3-edumazet@google.com>
Date: Mon, 15 Apr 2024 13:20:42 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: Jamal Hadi Salim <jhs@...atatu.com>, Cong Wang <xiyou.wangcong@...il.com>, 
	Jiri Pirko <jiri@...nulli.us>, netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 02/14] net_sched: cake: implement lockless cake_dump()

Instead of relying on RTNL, cake_dump() can use READ_ONCE()
annotations, paired with WRITE_ONCE() ones in cake_change().

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/sched/sch_cake.c | 98 +++++++++++++++++++++++++-------------------
 1 file changed, 55 insertions(+), 43 deletions(-)

diff --git a/net/sched/sch_cake.c b/net/sched/sch_cake.c
index 2eabc4dc5b79a83ce423f73c9cccec86f14be7cf..bb37a0dedcc1e4b3418f6681d87108aad7ea066f 100644
--- a/net/sched/sch_cake.c
+++ b/net/sched/sch_cake.c
@@ -2572,6 +2572,7 @@ static int cake_change(struct Qdisc *sch, struct nlattr *opt,
 {
 	struct cake_sched_data *q = qdisc_priv(sch);
 	struct nlattr *tb[TCA_CAKE_MAX + 1];
+	u16 rate_flags;
 	int err;
 
 	err = nla_parse_nested_deprecated(tb, TCA_CAKE_MAX, opt, cake_policy,
@@ -2592,16 +2593,19 @@ static int cake_change(struct Qdisc *sch, struct nlattr *opt,
 	}
 
 	if (tb[TCA_CAKE_BASE_RATE64])
-		q->rate_bps = nla_get_u64(tb[TCA_CAKE_BASE_RATE64]);
+		WRITE_ONCE(q->rate_bps,
+			   nla_get_u64(tb[TCA_CAKE_BASE_RATE64]));
 
 	if (tb[TCA_CAKE_DIFFSERV_MODE])
-		q->tin_mode = nla_get_u32(tb[TCA_CAKE_DIFFSERV_MODE]);
+		WRITE_ONCE(q->tin_mode,
+			   nla_get_u32(tb[TCA_CAKE_DIFFSERV_MODE]));
 
+	rate_flags = q->rate_flags;
 	if (tb[TCA_CAKE_WASH]) {
 		if (!!nla_get_u32(tb[TCA_CAKE_WASH]))
-			q->rate_flags |= CAKE_FLAG_WASH;
+			rate_flags |= CAKE_FLAG_WASH;
 		else
-			q->rate_flags &= ~CAKE_FLAG_WASH;
+			rate_flags &= ~CAKE_FLAG_WASH;
 	}
 
 	if (tb[TCA_CAKE_FLOW_MODE])
@@ -2610,11 +2614,13 @@ static int cake_change(struct Qdisc *sch, struct nlattr *opt,
 					CAKE_FLOW_MASK));
 
 	if (tb[TCA_CAKE_ATM])
-		q->atm_mode = nla_get_u32(tb[TCA_CAKE_ATM]);
+		WRITE_ONCE(q->atm_mode,
+			   nla_get_u32(tb[TCA_CAKE_ATM]));
 
 	if (tb[TCA_CAKE_OVERHEAD]) {
-		q->rate_overhead = nla_get_s32(tb[TCA_CAKE_OVERHEAD]);
-		q->rate_flags |= CAKE_FLAG_OVERHEAD;
+		WRITE_ONCE(q->rate_overhead,
+			   nla_get_s32(tb[TCA_CAKE_OVERHEAD]));
+		rate_flags |= CAKE_FLAG_OVERHEAD;
 
 		q->max_netlen = 0;
 		q->max_adjlen = 0;
@@ -2623,7 +2629,7 @@ static int cake_change(struct Qdisc *sch, struct nlattr *opt,
 	}
 
 	if (tb[TCA_CAKE_RAW]) {
-		q->rate_flags &= ~CAKE_FLAG_OVERHEAD;
+		rate_flags &= ~CAKE_FLAG_OVERHEAD;
 
 		q->max_netlen = 0;
 		q->max_adjlen = 0;
@@ -2632,54 +2638,57 @@ static int cake_change(struct Qdisc *sch, struct nlattr *opt,
 	}
 
 	if (tb[TCA_CAKE_MPU])
-		q->rate_mpu = nla_get_u32(tb[TCA_CAKE_MPU]);
+		WRITE_ONCE(q->rate_mpu,
+			   nla_get_u32(tb[TCA_CAKE_MPU]));
 
 	if (tb[TCA_CAKE_RTT]) {
-		q->interval = nla_get_u32(tb[TCA_CAKE_RTT]);
+		u32 interval = nla_get_u32(tb[TCA_CAKE_RTT]);
 
-		if (!q->interval)
-			q->interval = 1;
+		WRITE_ONCE(q->interval, max(interval, 1U));
 	}
 
 	if (tb[TCA_CAKE_TARGET]) {
-		q->target = nla_get_u32(tb[TCA_CAKE_TARGET]);
+		u32 target = nla_get_u32(tb[TCA_CAKE_TARGET]);
 
-		if (!q->target)
-			q->target = 1;
+		WRITE_ONCE(q->target, max(target, 1U));
 	}
 
 	if (tb[TCA_CAKE_AUTORATE]) {
 		if (!!nla_get_u32(tb[TCA_CAKE_AUTORATE]))
-			q->rate_flags |= CAKE_FLAG_AUTORATE_INGRESS;
+			rate_flags |= CAKE_FLAG_AUTORATE_INGRESS;
 		else
-			q->rate_flags &= ~CAKE_FLAG_AUTORATE_INGRESS;
+			rate_flags &= ~CAKE_FLAG_AUTORATE_INGRESS;
 	}
 
 	if (tb[TCA_CAKE_INGRESS]) {
 		if (!!nla_get_u32(tb[TCA_CAKE_INGRESS]))
-			q->rate_flags |= CAKE_FLAG_INGRESS;
+			rate_flags |= CAKE_FLAG_INGRESS;
 		else
-			q->rate_flags &= ~CAKE_FLAG_INGRESS;
+			rate_flags &= ~CAKE_FLAG_INGRESS;
 	}
 
 	if (tb[TCA_CAKE_ACK_FILTER])
-		q->ack_filter = nla_get_u32(tb[TCA_CAKE_ACK_FILTER]);
+		WRITE_ONCE(q->ack_filter,
+			   nla_get_u32(tb[TCA_CAKE_ACK_FILTER]));
 
 	if (tb[TCA_CAKE_MEMORY])
-		q->buffer_config_limit = nla_get_u32(tb[TCA_CAKE_MEMORY]);
+		WRITE_ONCE(q->buffer_config_limit,
+			   nla_get_u32(tb[TCA_CAKE_MEMORY]));
 
 	if (tb[TCA_CAKE_SPLIT_GSO]) {
 		if (!!nla_get_u32(tb[TCA_CAKE_SPLIT_GSO]))
-			q->rate_flags |= CAKE_FLAG_SPLIT_GSO;
+			rate_flags |= CAKE_FLAG_SPLIT_GSO;
 		else
-			q->rate_flags &= ~CAKE_FLAG_SPLIT_GSO;
+			rate_flags &= ~CAKE_FLAG_SPLIT_GSO;
 	}
 
 	if (tb[TCA_CAKE_FWMARK]) {
-		q->fwmark_mask = nla_get_u32(tb[TCA_CAKE_FWMARK]);
-		q->fwmark_shft = q->fwmark_mask ? __ffs(q->fwmark_mask) : 0;
+		WRITE_ONCE(q->fwmark_mask, nla_get_u32(tb[TCA_CAKE_FWMARK]));
+		WRITE_ONCE(q->fwmark_shft,
+			   q->fwmark_mask ? __ffs(q->fwmark_mask) : 0);
 	}
 
+	WRITE_ONCE(q->rate_flags, rate_flags);
 	if (q->tins) {
 		sch_tree_lock(sch);
 		cake_reconfigure(sch);
@@ -2774,68 +2783,71 @@ static int cake_dump(struct Qdisc *sch, struct sk_buff *skb)
 {
 	struct cake_sched_data *q = qdisc_priv(sch);
 	struct nlattr *opts;
+	u16 rate_flags;
 
 	opts = nla_nest_start_noflag(skb, TCA_OPTIONS);
 	if (!opts)
 		goto nla_put_failure;
 
-	if (nla_put_u64_64bit(skb, TCA_CAKE_BASE_RATE64, q->rate_bps,
-			      TCA_CAKE_PAD))
+	if (nla_put_u64_64bit(skb, TCA_CAKE_BASE_RATE64,
+			      READ_ONCE(q->rate_bps), TCA_CAKE_PAD))
 		goto nla_put_failure;
 
 	if (nla_put_u32(skb, TCA_CAKE_FLOW_MODE,
-			q->flow_mode & CAKE_FLOW_MASK))
+			READ_ONCE(q->flow_mode) & CAKE_FLOW_MASK))
 		goto nla_put_failure;
 
-	if (nla_put_u32(skb, TCA_CAKE_RTT, q->interval))
+	if (nla_put_u32(skb, TCA_CAKE_RTT, READ_ONCE(q->interval)))
 		goto nla_put_failure;
 
-	if (nla_put_u32(skb, TCA_CAKE_TARGET, q->target))
+	if (nla_put_u32(skb, TCA_CAKE_TARGET, READ_ONCE(q->target)))
 		goto nla_put_failure;
 
-	if (nla_put_u32(skb, TCA_CAKE_MEMORY, q->buffer_config_limit))
+	if (nla_put_u32(skb, TCA_CAKE_MEMORY,
+			READ_ONCE(q->buffer_config_limit)))
 		goto nla_put_failure;
 
+	rate_flags = READ_ONCE(q->rate_flags);
 	if (nla_put_u32(skb, TCA_CAKE_AUTORATE,
-			!!(q->rate_flags & CAKE_FLAG_AUTORATE_INGRESS)))
+			!!(rate_flags & CAKE_FLAG_AUTORATE_INGRESS)))
 		goto nla_put_failure;
 
 	if (nla_put_u32(skb, TCA_CAKE_INGRESS,
-			!!(q->rate_flags & CAKE_FLAG_INGRESS)))
+			!!(rate_flags & CAKE_FLAG_INGRESS)))
 		goto nla_put_failure;
 
-	if (nla_put_u32(skb, TCA_CAKE_ACK_FILTER, q->ack_filter))
+	if (nla_put_u32(skb, TCA_CAKE_ACK_FILTER, READ_ONCE(q->ack_filter)))
 		goto nla_put_failure;
 
 	if (nla_put_u32(skb, TCA_CAKE_NAT,
-			!!(q->flow_mode & CAKE_FLOW_NAT_FLAG)))
+			!!(READ_ONCE(q->flow_mode) & CAKE_FLOW_NAT_FLAG)))
 		goto nla_put_failure;
 
-	if (nla_put_u32(skb, TCA_CAKE_DIFFSERV_MODE, q->tin_mode))
+	if (nla_put_u32(skb, TCA_CAKE_DIFFSERV_MODE, READ_ONCE(q->tin_mode)))
 		goto nla_put_failure;
 
 	if (nla_put_u32(skb, TCA_CAKE_WASH,
-			!!(q->rate_flags & CAKE_FLAG_WASH)))
+			!!(rate_flags & CAKE_FLAG_WASH)))
 		goto nla_put_failure;
 
-	if (nla_put_u32(skb, TCA_CAKE_OVERHEAD, q->rate_overhead))
+	if (nla_put_u32(skb, TCA_CAKE_OVERHEAD, READ_ONCE(q->rate_overhead)))
 		goto nla_put_failure;
 
-	if (!(q->rate_flags & CAKE_FLAG_OVERHEAD))
+	if (!(rate_flags & CAKE_FLAG_OVERHEAD))
 		if (nla_put_u32(skb, TCA_CAKE_RAW, 0))
 			goto nla_put_failure;
 
-	if (nla_put_u32(skb, TCA_CAKE_ATM, q->atm_mode))
+	if (nla_put_u32(skb, TCA_CAKE_ATM, READ_ONCE(q->atm_mode)))
 		goto nla_put_failure;
 
-	if (nla_put_u32(skb, TCA_CAKE_MPU, q->rate_mpu))
+	if (nla_put_u32(skb, TCA_CAKE_MPU, READ_ONCE(q->rate_mpu)))
 		goto nla_put_failure;
 
 	if (nla_put_u32(skb, TCA_CAKE_SPLIT_GSO,
-			!!(q->rate_flags & CAKE_FLAG_SPLIT_GSO)))
+			!!(rate_flags & CAKE_FLAG_SPLIT_GSO)))
 		goto nla_put_failure;
 
-	if (nla_put_u32(skb, TCA_CAKE_FWMARK, q->fwmark_mask))
+	if (nla_put_u32(skb, TCA_CAKE_FWMARK, READ_ONCE(q->fwmark_mask)))
 		goto nla_put_failure;
 
 	return nla_nest_end(skb, opts);
-- 
2.44.0.683.g7961c838ac-goog


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