net: use reciprocal_scale() helper

Replace open codings of (((u64) <x> * <y>) >> 32) with reciprocal_scale().

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/dev.c

@@ -3124,8 +3124,7 @@ static int get_rps_cpu(struct net_device *dev, struct sk_buff *skb,
 	}
 
 	if (map) {
-		tcpu = map->cpus[((u64) hash * map->len) >> 32];
-
+		tcpu = map->cpus[reciprocal_scale(hash, map->len)];
 		if (cpu_online(tcpu)) {
 			cpu = tcpu;
 			goto done;

net/core/flow_dissector.c

@@ -298,7 +298,7 @@ u16 __skb_tx_hash(const struct net_device *dev, struct sk_buff *skb,
 		qcount = dev->tc_to_txq[tc].count;
 	}
 
-	return (u16) (((u64)skb_get_hash(skb) * qcount) >> 32) + qoffset;
+	return (u16) reciprocal_scale(skb_get_hash(skb), qcount) + qoffset;
 }
 EXPORT_SYMBOL(__skb_tx_hash);
 
@@ -371,9 +371,8 @@ static inline int get_xps_queue(struct net_device *dev, struct sk_buff *skb)
 			if (map->len == 1)
 				queue_index = map->queues[0];
 			else
-				queue_index = map->queues[
-				    ((u64)skb_get_hash(skb) * map->len) >> 32];
-
+				queue_index = map->queues[reciprocal_scale(skb_get_hash(skb),
+									   map->len)];
 			if (unlikely(queue_index >= dev->real_num_tx_queues))
 				queue_index = -1;
 		}

net/ipv4/inet_hashtables.c

@@ -229,7 +229,7 @@ begin:
 			}
 		} else if (score == hiscore && reuseport) {
 			matches++;
-			if (((u64)phash * matches) >> 32 == 0)
+			if (reciprocal_scale(phash, matches) == 0)
 				result = sk;
 			phash = next_pseudo_random32(phash);
 		}

net/ipv4/netfilter/ipt_CLUSTERIP.c

@@ -285,7 +285,7 @@ clusterip_hashfn(const struct sk_buff *skb,
 	}
 
 	/* node numbers are 1..n, not 0..n */
-	return (((u64)hashval * config->num_total_nodes) >> 32) + 1;
+	return reciprocal_scale(hashval, config->num_total_nodes) + 1;
 }
 
 static inline int

net/ipv4/udp.c

@@ -224,7 +224,7 @@ int udp_lib_get_port(struct sock *sk, unsigned short snum,
 		remaining = (high - low) + 1;
 
 		rand = prandom_u32();
-		first = (((u64)rand * remaining) >> 32) + low;
+		first = reciprocal_scale(rand, remaining) + low;
 		/*
 		 * force rand to be an odd multiple of UDP_HTABLE_SIZE
 		 */
@@ -448,7 +448,7 @@ begin:
 			}
 		} else if (score == badness && reuseport) {
 			matches++;
-			if (((u64)hash * matches) >> 32 == 0)
+			if (reciprocal_scale(hash, matches) == 0)
 				result = sk;
 			hash = next_pseudo_random32(hash);
 		}
@@ -529,7 +529,7 @@ begin:
 			}
 		} else if (score == badness && reuseport) {
 			matches++;
-			if (((u64)hash * matches) >> 32 == 0)
+			if (reciprocal_scale(hash, matches) == 0)
 				result = sk;
 			hash = next_pseudo_random32(hash);
 		}

net/ipv6/inet6_hashtables.c

@@ -198,7 +198,7 @@ begin:
 			}
 		} else if (score == hiscore && reuseport) {
 			matches++;
-			if (((u64)phash * matches) >> 32 == 0)
+			if (reciprocal_scale(phash, matches) == 0)
 				result = sk;
 			phash = next_pseudo_random32(phash);
 		}

net/ipv6/udp.c

@@ -243,7 +243,7 @@ begin:
 				goto exact_match;
 		} else if (score == badness && reuseport) {
 			matches++;
-			if (((u64)hash * matches) >> 32 == 0)
+			if (reciprocal_scale(hash, matches) == 0)
 				result = sk;
 			hash = next_pseudo_random32(hash);
 		}
@@ -323,7 +323,7 @@ begin:
 			}
 		} else if (score == badness && reuseport) {
 			matches++;
-			if (((u64)hash * matches) >> 32 == 0)
+			if (reciprocal_scale(hash, matches) == 0)
 				result = sk;
 			hash = next_pseudo_random32(hash);
 		}

net/netfilter/nf_conntrack_core.c

@@ -142,7 +142,7 @@ static u32 hash_conntrack_raw(const struct nf_conntrack_tuple *tuple, u16 zone)
 
 static u32 __hash_bucket(u32 hash, unsigned int size)
 {
-	return ((u64)hash * size) >> 32;
+	return reciprocal_scale(hash, size);
 }
 
 static u32 hash_bucket(u32 hash, const struct net *net)

net/netfilter/nf_conntrack_expect.c

@@ -83,7 +83,8 @@ static unsigned int nf_ct_expect_dst_hash(const struct nf_conntrack_tuple *tuple
 	hash = jhash2(tuple->dst.u3.all, ARRAY_SIZE(tuple->dst.u3.all),
 		      (((tuple->dst.protonum ^ tuple->src.l3num) << 16) |
 		       (__force __u16)tuple->dst.u.all) ^ nf_conntrack_hash_rnd);
-	return ((u64)hash * nf_ct_expect_hsize) >> 32;
+
+	return reciprocal_scale(hash, nf_ct_expect_hsize);
 }
 
 struct nf_conntrack_expect *

net/netfilter/nf_nat_core.c

@@ -126,7 +126,8 @@ hash_by_src(const struct net *net, u16 zone,
 	/* Original src, to ensure we map it consistently if poss. */
 	hash = jhash2((u32 *)&tuple->src, sizeof(tuple->src) / sizeof(u32),
 		      tuple->dst.protonum ^ zone ^ nf_conntrack_hash_rnd);
-	return ((u64)hash * net->ct.nat_htable_size) >> 32;
+
+	return reciprocal_scale(hash, net->ct.nat_htable_size);
 }
 
 /* Is this tuple already taken? (not by us) */
@@ -274,7 +275,7 @@ find_best_ips_proto(u16 zone, struct nf_conntrack_tuple *tuple,
 		}
 
 		var_ipp->all[i] = (__force __u32)
-			htonl(minip + (((u64)j * dist) >> 32));
+			htonl(minip + reciprocal_scale(j, dist));
 		if (var_ipp->all[i] != range->max_addr.all[i])
 			full_range = true;
 

net/netfilter/xt_HMARK.c

@@ -126,7 +126,7 @@ hmark_hash(struct hmark_tuple *t, const struct xt_hmark_info *info)
 	hash = jhash_3words(src, dst, t->uports.v32, info->hashrnd);
 	hash = hash ^ (t->proto & info->proto_mask);
 
-	return (((u64)hash * info->hmodulus) >> 32) + info->hoffset;
+	return reciprocal_scale(hash, info->hmodulus) + info->hoffset;
 }
 
 static void

net/netfilter/xt_cluster.c

@@ -55,7 +55,8 @@ xt_cluster_hash(const struct nf_conn *ct,
 		WARN_ON(1);
 		break;
 	}
-	return (((u64)hash * info->total_nodes) >> 32);
+
+	return reciprocal_scale(hash, info->total_nodes);
 }
 
 static inline bool

net/netfilter/xt_hashlimit.c

@@ -135,7 +135,7 @@ hash_dst(const struct xt_hashlimit_htable *ht, const struct dsthash_dst *dst)
 	 * give results between [0 and cfg.size-1] and same hash distribution,
 	 * but using a multiply, less expensive than a divide
 	 */
-	return ((u64)hash * ht->cfg.size) >> 32;
+	return reciprocal_scale(hash, ht->cfg.size);
 }
 
 static struct dsthash_ent *

net/sched/sch_fq_codel.c

@@ -77,7 +77,8 @@ static unsigned int fq_codel_hash(const struct fq_codel_sched_data *q,
 	hash = jhash_3words((__force u32)keys.dst,
 			    (__force u32)keys.src ^ keys.ip_proto,
 			    (__force u32)keys.ports, q->perturbation);
-	return ((u64)hash * q->flows_cnt) >> 32;
+
+	return reciprocal_scale(hash, q->flows_cnt);
 }
 
 static unsigned int fq_codel_classify(struct sk_buff *skb, struct Qdisc *sch,