Merge branch 'rps-misc-changes'

Eric Dumazet says:

====================
rps: misc changes

Minor changes in rps:

skb_flow_limit() is probably unused these days,
and data-races are quite theoretical.
====================

Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: kuba-moo

include/net/rps.h

@@ -57,9 +57,10 @@ struct rps_dev_flow_table {
  * meaning we use 32-6=26 bits for the hash.
  */
 struct rps_sock_flow_table {
-	u32	mask;
+	struct rcu_head	rcu;
+	u32		mask;
 
-	u32	ents[] ____cacheline_aligned_in_smp;
+	u32		ents[] ____cacheline_aligned_in_smp;
 };
 #define	RPS_SOCK_FLOW_TABLE_SIZE(_num) (offsetof(struct rps_sock_flow_table, ents[_num]))
 

net/core/dev.c

@@ -4953,7 +4953,8 @@ static void rps_trigger_softirq(void *data)
 	struct softnet_data *sd = data;
 
 	____napi_schedule(sd, &sd->backlog);
-	sd->received_rps++;
+	/* Pairs with READ_ONCE() in softnet_seq_show() */
+	WRITE_ONCE(sd->received_rps, sd->received_rps + 1);
 }
 
 #endif /* CONFIG_RPS */
@@ -5038,7 +5039,7 @@ static bool skb_flow_limit(struct sk_buff *skb, unsigned int qlen)
 	rcu_read_lock();
 	fl = rcu_dereference(sd->flow_limit);
 	if (fl) {
-		new_flow = skb_get_hash(skb) & (fl->num_buckets - 1);
+		new_flow = hash_32(skb_get_hash(skb), fl->log_buckets);
 		old_flow = fl->history[fl->history_head];
 		fl->history[fl->history_head] = new_flow;
 
@@ -5049,7 +5050,8 @@ static bool skb_flow_limit(struct sk_buff *skb, unsigned int qlen)
 			fl->buckets[old_flow]--;
 
 		if (++fl->buckets[new_flow] > (FLOW_LIMIT_HISTORY >> 1)) {
-			fl->count++;
+			/* Pairs with READ_ONCE() in softnet_seq_show() */
+			WRITE_ONCE(fl->count, fl->count + 1);
 			rcu_read_unlock();
 			return true;
 		}
@@ -7522,7 +7524,8 @@ static __latent_entropy void net_rx_action(void)
 		 */
 		if (unlikely(budget <= 0 ||
 			     time_after_eq(jiffies, time_limit))) {
-			sd->time_squeeze++;
+			/* Pairs with READ_ONCE() in softnet_seq_show() */
+			WRITE_ONCE(sd->time_squeeze, sd->time_squeeze + 1);
 			break;
 		}
 	}

net/core/dev.h

@@ -15,8 +15,9 @@ struct cpumask;
 /* Random bits of netdevice that don't need to be exposed */
 #define FLOW_LIMIT_HISTORY	(1 << 7)  /* must be ^2 and !overflow buckets */
 struct sd_flow_limit {
-	u64			count;
-	unsigned int		num_buckets;
+	struct rcu_head		rcu;
+	unsigned int		count;
+	u8			log_buckets;
 	unsigned int		history_head;
 	u16			history[FLOW_LIMIT_HISTORY];
 	u8			buckets[];

net/core/net-procfs.c

@@ -132,8 +132,9 @@ static int softnet_seq_show(struct seq_file *seq, void *v)
 
 	rcu_read_lock();
 	fl = rcu_dereference(sd->flow_limit);
+	/* Pairs with WRITE_ONCE() in skb_flow_limit() */
 	if (fl)
-		flow_limit_count = fl->count;
+		flow_limit_count = READ_ONCE(fl->count);
 	rcu_read_unlock();
 #endif
 
@@ -144,11 +145,11 @@ static int softnet_seq_show(struct seq_file *seq, void *v)
 	seq_printf(seq,
 		   "%08x %08x %08x %08x %08x %08x %08x %08x %08x %08x %08x %08x %08x "
 		   "%08x %08x\n",
-		   sd->processed, atomic_read(&sd->dropped),
-		   sd->time_squeeze, 0,
+		   READ_ONCE(sd->processed), atomic_read(&sd->dropped),
+		   READ_ONCE(sd->time_squeeze), 0,
 		   0, 0, 0, 0, /* was fastroute */
 		   0,	/* was cpu_collision */
-		   sd->received_rps, flow_limit_count,
+		   READ_ONCE(sd->received_rps), flow_limit_count,
 		   input_qlen + process_qlen, (int)seq->index,
 		   input_qlen, process_qlen);
 	return 0;

net/core/sysctl_net_core.c

@@ -201,7 +201,7 @@ static int rps_sock_flow_sysctl(const struct ctl_table *table, int write,
 			if (orig_sock_table) {
 				static_branch_dec(&rps_needed);
 				static_branch_dec(&rfs_needed);
-				kvfree_rcu_mightsleep(orig_sock_table);
+				kvfree_rcu(orig_sock_table, rcu);
 			}
 		}
 	}
@@ -239,7 +239,7 @@ static int flow_limit_cpu_sysctl(const struct ctl_table *table, int write,
 				     lockdep_is_held(&flow_limit_update_mutex));
 			if (cur && !cpumask_test_cpu(i, mask)) {
 				RCU_INIT_POINTER(sd->flow_limit, NULL);
-				kfree_rcu_mightsleep(cur);
+				kfree_rcu(cur, rcu);
 			} else if (!cur && cpumask_test_cpu(i, mask)) {
 				cur = kzalloc_node(len, GFP_KERNEL,
 						   cpu_to_node(i));
@@ -248,7 +248,7 @@ static int flow_limit_cpu_sysctl(const struct ctl_table *table, int write,
 					ret = -ENOMEM;
 					goto write_unlock;
 				}
-				cur->num_buckets = netdev_flow_limit_table_len;
+				cur->log_buckets = ilog2(netdev_flow_limit_table_len);
 				rcu_assign_pointer(sd->flow_limit, cur);
 			}
 		}