Currently this size is 16, but as the comment says this
is so only because all the chains (except one) has the
length 1. I think, that some day this may change, so 
growing this hash will be much easier.

Besides, symbolic names are read better than magic constants.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>

---

diff --git a/net/core/dev.c b/net/core/dev.c
index 043e2f8..d88d832 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -150,8 +150,11 @@
  *		86DD	IPv6
  */
 
+#define PTYPE_HASH_SIZE	(16)
+#define PTYPE_HASH_MASK	(PTYPE_HASH_SIZE - 1)
+
 static DEFINE_SPINLOCK(ptype_lock);
-static struct list_head ptype_base[16] __read_mostly;	/* 16 way hashed list */
+static struct list_head ptype_base[PTYPE_HASH_SIZE] __read_mostly;
 static struct list_head ptype_all __read_mostly;	/* Taps */
 
 #ifdef CONFIG_NET_DMA
@@ -362,7 +365,7 @@ void dev_add_pack(struct packet_type *pt)
 	if (pt->type == htons(ETH_P_ALL))
 		list_add_rcu(&pt->list, &ptype_all);
 	else {
-		hash = ntohs(pt->type) & 15;
+		hash = ntohs(pt->type) & PTYPE_HASH_MASK;
 		list_add_rcu(&pt->list, &ptype_base[hash]);
 	}
 	spin_unlock_bh(&ptype_lock);
@@ -391,7 +394,7 @@ void __dev_remove_pack(struct packet_type *pt)
 	if (pt->type == htons(ETH_P_ALL))
 		head = &ptype_all;
 	else
-		head = &ptype_base[ntohs(pt->type) & 15];
+		head = &ptype_base[ntohs(pt->type) & PTYPE_HASH_MASK];
 
 	list_for_each_entry(pt1, head, list) {
 		if (pt == pt1) {
@@ -1420,7 +1423,8 @@ struct sk_buff *skb_gso_segment(struct sk_buff *skb, int features)
 	}
 
 	rcu_read_lock();
-	list_for_each_entry_rcu(ptype, &ptype_base[ntohs(type) & 15], list) {
+	list_for_each_entry_rcu(ptype,
+			&ptype_base[ntohs(type) & PTYPE_HASH_MASK], list) {
 		if (ptype->type == type && !ptype->dev && ptype->gso_segment) {
 			if (unlikely(skb->ip_summed != CHECKSUM_PARTIAL)) {
 				err = ptype->gso_send_check(skb);
@@ -2077,7 +2081,8 @@ ncls:
 		goto out;
 
 	type = skb->protocol;
-	list_for_each_entry_rcu(ptype, &ptype_base[ntohs(type)&15], list) {
+	list_for_each_entry_rcu(ptype,
+			&ptype_base[ntohs(type) & PTYPE_HASH_MASK], list) {
 		if (ptype->type == type &&
 		    (!ptype->dev || ptype->dev == skb->dev)) {
 			if (pt_prev)
@@ -2521,7 +2526,7 @@ static void *ptype_get_idx(loff_t pos)
 		++i;
 	}
 
-	for (t = 0; t < 16; t++) {
+	for (t = 0; t < PTYPE_HASH_SIZE; t++) {
 		list_for_each_entry_rcu(pt, &ptype_base[t], list) {
 			if (i == pos)
 				return pt;
@@ -2555,10 +2560,10 @@ static void *ptype_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 		hash = 0;
 		nxt = ptype_base[0].next;
 	} else
-		hash = ntohs(pt->type) & 15;
+		hash = ntohs(pt->type) & PTYPE_HASH_MASK;
 
 	while (nxt == &ptype_base[hash]) {
-		if (++hash >= 16)
+		if (++hash >= PTYPE_HASH_SIZE)
 			return NULL;
 		nxt = ptype_base[hash].next;
 	}
@@ -4396,7 +4401,7 @@ static int __init net_dev_init(void)
 		goto out;
 
 	INIT_LIST_HEAD(&ptype_all);
-	for (i = 0; i < 16; i++)
+	for (i = 0; i < PTYPE_HASH_SIZE; i++)
 		INIT_LIST_HEAD(&ptype_base[i]);
 
 	if (register_pernet_subsys(&netdev_net_ops))
-- 
1.5.3.4

On Fri, Nov 23, 2007 at 04:47:36PM +0300, Pavel Emelyanov wrote:
> Currently this size is 16, but as the comment says this
> is so only because all the chains (except one) has the
> length 1. I think, that some day this may change, so 
> growing this hash will be much easier.
> 
> Besides, symbolic names are read better than magic constants.
> 
> Signed-off-by: Pavel Emelyanov <xemul@openvz.org>

Applied to net-2.6.25.  Thanks!
-- 
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