batman-adv: Directly print to seq_file in vis

The vis output doesn't need to be buffered in an character buffer before it can
be send to the userspace program that reads from the vis debug file.
Signed-off-by: NSven Eckelmann <sven@narfation.org>

net/batman-adv/vis.c

@@ -140,72 +140,117 @@ static void batadv_vis_data_insert_interface(const uint8_t *interface,
 	hlist_add_head(&entry->list, if_list);
 }
 
-static ssize_t batadv_vis_prim_sec(char *buff, const struct hlist_head *if_list)
+static void batadv_vis_data_read_prim_sec(struct seq_file *seq,
+					  const struct hlist_head *if_list)
 {
 	struct if_list_entry *entry;
 	struct hlist_node *pos;
-	size_t len = 0;
 
 	hlist_for_each_entry(entry, pos, if_list, list) {
 		if (entry->primary)
-			len += sprintf(buff + len, "PRIMARY, ");
+			seq_printf(seq, "PRIMARY, ");
 		else
-			len += sprintf(buff + len,  "SEC %pM, ", entry->addr);
+			seq_printf(seq,  "SEC %pM, ", entry->addr);
 	}
+}
+
+/* read an entry  */
+static ssize_t batadv_vis_data_read_entry(struct seq_file *seq,
+					  const struct vis_info_entry *entry,
+					  const uint8_t *src, bool primary)
+{
+	if (primary && entry->quality == 0)
+		return seq_printf(seq, "TT %pM, ", entry->dest);
+	else if (batadv_compare_eth(entry->src, src))
+		return seq_printf(seq, "TQ %pM %d, ", entry->dest,
+				  entry->quality);
+
+	return 0;
+}
+
+static void batadv_vis_data_insert_interfaces(struct hlist_head *list,
+					      struct vis_packet *packet,
+					      struct vis_info_entry *entries)
+{
+	int i;
+
+	for (i = 0; i < packet->entries; i++) {
+		if (entries[i].quality == 0)
+			continue;
 
-	return len;
+		if (batadv_compare_eth(entries[i].src, packet->vis_orig))
+			continue;
+
+		batadv_vis_data_insert_interface(entries[i].src, list, false);
+	}
 }
 
-static size_t batadv_vis_cnt_prim_sec(struct hlist_head *if_list)
+static void batadv_vis_data_read_entries(struct seq_file *seq,
+					 struct hlist_head *list,
+					 struct vis_packet *packet,
+					 struct vis_info_entry *entries)
 {
+	int i;
 	struct if_list_entry *entry;
 	struct hlist_node *pos;
-	size_t count = 0;
 
-	hlist_for_each_entry(entry, pos, if_list, list) {
-		if (entry->primary)
-			count += 9;
-		else
-			count += 23;
-	}
+	hlist_for_each_entry(entry, pos, list, list) {
+		seq_printf(seq, "%pM,", entry->addr);
+
+		for (i = 0; i < packet->entries; i++)
+			batadv_vis_data_read_entry(seq, &entries[i],
+						   entry->addr, entry->primary);
 
-	return count;
+		/* add primary/secondary records */
+		if (batadv_compare_eth(entry->addr, packet->vis_orig))
+			batadv_vis_data_read_prim_sec(seq, list);
+
+		seq_printf(seq, "\n");
+	}
 }
 
-/* read an entry  */
-static ssize_t batadv_vis_data_read_entry(char *buff,
-					  const struct vis_info_entry *entry,
-					  const uint8_t *src, bool primary)
+static void batadv_vis_seq_print_text_bucket(struct seq_file *seq,
+					     const struct hlist_head *head)
 {
-	/* maximal length: max(4+17+2, 3+17+1+3+2) == 26 */
-	if (primary && entry->quality == 0)
-		return sprintf(buff, "TT %pM, ", entry->dest);
-	else if (batadv_compare_eth(entry->src, src))
-		return sprintf(buff, "TQ %pM %d, ", entry->dest,
-			       entry->quality);
+	struct hlist_node *node;
+	struct vis_info *info;
+	struct vis_packet *packet;
+	uint8_t *entries_pos;
+	struct vis_info_entry *entries;
+	struct if_list_entry *entry;
+	struct hlist_node *pos, *n;
 
-	return 0;
+	HLIST_HEAD(vis_if_list);
+
+	hlist_for_each_entry_rcu(info, node, head, hash_entry) {
+		packet = (struct vis_packet *)info->skb_packet->data;
+		entries_pos = (uint8_t *)packet + sizeof(*packet);
+		entries = (struct vis_info_entry *)entries_pos;
+
+		batadv_vis_data_insert_interface(packet->vis_orig, &vis_if_list,
+						 true);
+		batadv_vis_data_insert_interfaces(&vis_if_list, packet,
+						  entries);
+		batadv_vis_data_read_entries(seq, &vis_if_list, packet,
+					     entries);
+
+		hlist_for_each_entry_safe(entry, pos, n, &vis_if_list, list) {
+			hlist_del(&entry->list);
+			kfree(entry);
+		}
+	}
 }
 
 int batadv_vis_seq_print_text(struct seq_file *seq, void *offset)
 {
 	struct hard_iface *primary_if;
-	struct hlist_node *node;
 	struct hlist_head *head;
-	struct vis_info *info;
-	struct vis_packet *packet;
-	struct vis_info_entry *entries;
 	struct net_device *net_dev = (struct net_device *)seq->private;
 	struct bat_priv *bat_priv = netdev_priv(net_dev);
 	struct hashtable_t *hash = bat_priv->vis_hash;
-	HLIST_HEAD(vis_if_list);
-	struct if_list_entry *entry;
-	struct hlist_node *pos, *n;
 	uint32_t i;
-	int j, ret = 0;
+	int ret = 0;
 	int vis_server = atomic_read(&bat_priv->vis_mode);
-	size_t buff_pos, buf_size;
-	char *buff;
 
 	primary_if = batadv_primary_if_get_selected(bat_priv);
 	if (!primary_if)
@@ -214,120 +259,13 @@ int batadv_vis_seq_print_text(struct seq_file *seq, void *offset)
 	if (vis_server == VIS_TYPE_CLIENT_UPDATE)
 		goto out;
 
-	buf_size = 1;
-	/* Estimate length */
 	spin_lock_bh(&bat_priv->vis_hash_lock);
 	for (i = 0; i < hash->size; i++) {
 		head = &hash->table[i];
-
-		rcu_read_lock();
-		hlist_for_each_entry_rcu(info, node, head, hash_entry) {
-			packet = (struct vis_packet *)info->skb_packet->data;
-			entries = (struct vis_info_entry *)
-				((char *)packet + sizeof(*packet));
-
-			batadv_vis_data_insert_interface(packet->vis_orig,
-							 &vis_if_list, true);
-
-			for (j = 0; j < packet->entries; j++) {
-				if (entries[j].quality == 0)
-					continue;
-				if (batadv_compare_eth(entries[j].src,
-						       packet->vis_orig))
-					continue;
-				batadv_vis_data_insert_interface(entries[j].src,
-								 &vis_if_list,
-								 false);
-			}
-
-			hlist_for_each_entry(entry, pos, &vis_if_list, list) {
-				buf_size += 18 + 26 * packet->entries;
-
-				/* add primary/secondary records */
-				if (batadv_compare_eth(entry->addr,
-						       packet->vis_orig))
-					buf_size +=
-					  batadv_vis_cnt_prim_sec(&vis_if_list);
-
-				buf_size += 1;
-			}
-
-			hlist_for_each_entry_safe(entry, pos, n, &vis_if_list,
-						  list) {
-				hlist_del(&entry->list);
-				kfree(entry);
-			}
-		}
-		rcu_read_unlock();
+		batadv_vis_seq_print_text_bucket(seq, head);
 	}
-
-	buff = kmalloc(buf_size, GFP_ATOMIC);
-	if (!buff) {
-		spin_unlock_bh(&bat_priv->vis_hash_lock);
-		ret = -ENOMEM;
-		goto out;
-	}
-	buff[0] = '\0';
-	buff_pos = 0;
-
-	for (i = 0; i < hash->size; i++) {
-		head = &hash->table[i];
-
-		rcu_read_lock();
-		hlist_for_each_entry_rcu(info, node, head, hash_entry) {
-			packet = (struct vis_packet *)info->skb_packet->data;
-			entries = (struct vis_info_entry *)
-				((char *)packet + sizeof(*packet));
-
-			batadv_vis_data_insert_interface(packet->vis_orig,
-							 &vis_if_list, true);
-
-			for (j = 0; j < packet->entries; j++) {
-				if (entries[j].quality == 0)
-					continue;
-				if (batadv_compare_eth(entries[j].src,
-						       packet->vis_orig))
-					continue;
-				batadv_vis_data_insert_interface(entries[j].src,
-								 &vis_if_list,
-								 false);
-			}
-
-			hlist_for_each_entry(entry, pos, &vis_if_list, list) {
-				buff_pos += sprintf(buff + buff_pos, "%pM,",
-						entry->addr);
-
-				for (j = 0; j < packet->entries; j++)
-					buff_pos += batadv_vis_data_read_entry(
-							buff + buff_pos,
-							&entries[j],
-							entry->addr,
-							entry->primary);
-
-				/* add primary/secondary records */
-				if (batadv_compare_eth(entry->addr,
-						       packet->vis_orig))
-					buff_pos +=
-					 batadv_vis_prim_sec(buff + buff_pos,
-							     &vis_if_list);
-
-				buff_pos += sprintf(buff + buff_pos, "\n");
-			}
-
-			hlist_for_each_entry_safe(entry, pos, n, &vis_if_list,
-						  list) {
-				hlist_del(&entry->list);
-				kfree(entry);
-			}
-		}
-		rcu_read_unlock();
-	}
-
 	spin_unlock_bh(&bat_priv->vis_hash_lock);
 
-	seq_printf(seq, "%s", buff);
-	kfree(buff);
-
 out:
 	if (primary_if)
 		batadv_hardif_free_ref(primary_if);