ipv6: avoid high order memory allocations for /proc/net/ipv6_route

Dumping routes on a system with lots rt6_infos in the fibs causes up to
11-order allocations in seq_file (which fail). While we could switch
there to vmalloc we could just implement the streaming interface for
/proc/net/ipv6_route. This patch switches /proc/net/ipv6_route from
single_open_net to seq_open_net.

loff_t *pos tracks dst entries.

Also kill never used struct rt6_proc_arg and now unused function
fib6_clean_all_ro.

Cc: Ben Greear <greearb@candelatech.com>
Cc: Patrick McHardy <kaber@trash.net>
Cc: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/ip6_fib.h

@@ -280,10 +280,6 @@ struct fib6_node *fib6_locate(struct fib6_node *root,
 			      const struct in6_addr *daddr, int dst_len,
 			      const struct in6_addr *saddr, int src_len);
 
-void fib6_clean_all_ro(struct net *net,
-		       int (*func)(struct rt6_info *, void *arg),
-		       int prune, void *arg);
-
 void fib6_clean_all(struct net *net, int (*func)(struct rt6_info *, void *arg),
 		    int prune, void *arg);
 
@@ -299,6 +295,8 @@ void fib6_gc_cleanup(void);
 
 int fib6_init(void);
 
+int ipv6_route_open(struct inode *inode, struct file *file);
+
 #ifdef CONFIG_IPV6_MULTIPLE_TABLES
 int fib6_rules_init(void);
 void fib6_rules_cleanup(void);

net/ipv6/ip6_fib.c

@@ -1529,25 +1529,6 @@ static void fib6_clean_tree(struct net *net, struct fib6_node *root,
 	fib6_walk(&c.w);
 }
 
-void fib6_clean_all_ro(struct net *net, int (*func)(struct rt6_info *, void *arg),
-		    int prune, void *arg)
-{
-	struct fib6_table *table;
-	struct hlist_head *head;
-	unsigned int h;
-
-	rcu_read_lock();
-	for (h = 0; h < FIB6_TABLE_HASHSZ; h++) {
-		head = &net->ipv6.fib_table_hash[h];
-		hlist_for_each_entry_rcu(table, head, tb6_hlist) {
-			read_lock_bh(&table->tb6_lock);
-			fib6_clean_tree(net, &table->tb6_root,
-					func, prune, arg);
-			read_unlock_bh(&table->tb6_lock);
-		}
-	}
-	rcu_read_unlock();
-}
 void fib6_clean_all(struct net *net, int (*func)(struct rt6_info *, void *arg),
 		    int prune, void *arg)
 {
@@ -1782,3 +1763,175 @@ void fib6_gc_cleanup(void)
 	unregister_pernet_subsys(&fib6_net_ops);
 	kmem_cache_destroy(fib6_node_kmem);
 }
+
+#ifdef CONFIG_PROC_FS
+
+struct ipv6_route_iter {
+	struct seq_net_private p;
+	struct fib6_walker_t w;
+	loff_t skip;
+	struct fib6_table *tbl;
+};
+
+static int ipv6_route_seq_show(struct seq_file *seq, void *v)
+{
+	struct rt6_info *rt = v;
+	struct ipv6_route_iter *iter = seq->private;
+
+	seq_printf(seq, "%pi6 %02x ", &rt->rt6i_dst.addr, rt->rt6i_dst.plen);
+
+#ifdef CONFIG_IPV6_SUBTREES
+	seq_printf(seq, "%pi6 %02x ", &rt->rt6i_src.addr, rt->rt6i_src.plen);
+#else
+	seq_puts(seq, "00000000000000000000000000000000 00 ");
+#endif
+	if (rt->rt6i_flags & RTF_GATEWAY)
+		seq_printf(seq, "%pi6", &rt->rt6i_gateway);
+	else
+		seq_puts(seq, "00000000000000000000000000000000");
+
+	seq_printf(seq, " %08x %08x %08x %08x %8s\n",
+		   rt->rt6i_metric, atomic_read(&rt->dst.__refcnt),
+		   rt->dst.__use, rt->rt6i_flags,
+		   rt->dst.dev ? rt->dst.dev->name : "");
+	iter->w.leaf = NULL;
+	return 0;
+}
+
+static int ipv6_route_yield(struct fib6_walker_t *w)
+{
+	struct ipv6_route_iter *iter = w->args;
+
+	if (!iter->skip)
+		return 1;
+
+	do {
+		iter->w.leaf = iter->w.leaf->dst.rt6_next;
+		iter->skip--;
+		if (!iter->skip && iter->w.leaf)
+			return 1;
+	} while (iter->w.leaf);
+
+	return 0;
+}
+
+static void ipv6_route_seq_setup_walk(struct ipv6_route_iter *iter)
+{
+	memset(&iter->w, 0, sizeof(iter->w));
+	iter->w.func = ipv6_route_yield;
+	iter->w.root = &iter->tbl->tb6_root;
+	iter->w.state = FWS_INIT;
+	iter->w.node = iter->w.root;
+	iter->w.args = iter;
+	INIT_LIST_HEAD(&iter->w.lh);
+	fib6_walker_link(&iter->w);
+}
+
+static struct fib6_table *ipv6_route_seq_next_table(struct fib6_table *tbl,
+						    struct net *net)
+{
+	unsigned int h;
+	struct hlist_node *node;
+
+	if (tbl) {
+		h = (tbl->tb6_id & (FIB6_TABLE_HASHSZ - 1)) + 1;
+		node = rcu_dereference_bh(hlist_next_rcu(&tbl->tb6_hlist));
+	} else {
+		h = 0;
+		node = NULL;
+	}
+
+	while (!node && h < FIB6_TABLE_HASHSZ) {
+		node = rcu_dereference_bh(
+			hlist_first_rcu(&net->ipv6.fib_table_hash[h++]));
+	}
+	return hlist_entry_safe(node, struct fib6_table, tb6_hlist);
+}
+
+static void *ipv6_route_seq_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+	int r;
+	struct rt6_info *n;
+	struct net *net = seq_file_net(seq);
+	struct ipv6_route_iter *iter = seq->private;
+
+	if (!v)
+		goto iter_table;
+
+	n = ((struct rt6_info *)v)->dst.rt6_next;
+	if (n) {
+		++*pos;
+		return n;
+	}
+
+iter_table:
+	read_lock(&iter->tbl->tb6_lock);
+	r = fib6_walk_continue(&iter->w);
+	read_unlock(&iter->tbl->tb6_lock);
+	if (r > 0) {
+		if (v)
+			++*pos;
+		return iter->w.leaf;
+	} else if (r < 0) {
+		fib6_walker_unlink(&iter->w);
+		return NULL;
+	}
+	fib6_walker_unlink(&iter->w);
+
+	iter->tbl = ipv6_route_seq_next_table(iter->tbl, net);
+	if (!iter->tbl)
+		return NULL;
+
+	ipv6_route_seq_setup_walk(iter);
+	goto iter_table;
+}
+
+static void *ipv6_route_seq_start(struct seq_file *seq, loff_t *pos)
+	__acquires(RCU_BH)
+{
+	struct net *net = seq_file_net(seq);
+	struct ipv6_route_iter *iter = seq->private;
+
+	rcu_read_lock_bh();
+	iter->tbl = ipv6_route_seq_next_table(NULL, net);
+	iter->skip = *pos;
+
+	if (iter->tbl) {
+		ipv6_route_seq_setup_walk(iter);
+		return ipv6_route_seq_next(seq, NULL, pos);
+	} else {
+		return NULL;
+	}
+}
+
+static bool ipv6_route_iter_active(struct ipv6_route_iter *iter)
+{
+	struct fib6_walker_t *w = &iter->w;
+	return w->node && !(w->state == FWS_U && w->node == w->root);
+}
+
+static void ipv6_route_seq_stop(struct seq_file *seq, void *v)
+	__releases(RCU_BH)
+{
+	struct ipv6_route_iter *iter = seq->private;
+
+	if (ipv6_route_iter_active(iter))
+		fib6_walker_unlink(&iter->w);
+
+	rcu_read_unlock_bh();
+}
+
+static const struct seq_operations ipv6_route_seq_ops = {
+	.start	= ipv6_route_seq_start,
+	.next	= ipv6_route_seq_next,
+	.stop	= ipv6_route_seq_stop,
+	.show	= ipv6_route_seq_show
+};
+
+int ipv6_route_open(struct inode *inode, struct file *file)
+{
+	return seq_open_net(inode, file, &ipv6_route_seq_ops,
+			    sizeof(struct ipv6_route_iter));
+}
+
+#endif /* CONFIG_PROC_FS */

net/ipv6/route.c

@@ -2800,56 +2800,12 @@ static int ip6_route_dev_notify(struct notifier_block *this,
 
 #ifdef CONFIG_PROC_FS
 
-struct rt6_proc_arg
-{
-	char *buffer;
-	int offset;
-	int length;
-	int skip;
-	int len;
-};
-
-static int rt6_info_route(struct rt6_info *rt, void *p_arg)
-{
-	struct seq_file *m = p_arg;
-
-	seq_printf(m, "%pi6 %02x ", &rt->rt6i_dst.addr, rt->rt6i_dst.plen);
-
-#ifdef CONFIG_IPV6_SUBTREES
-	seq_printf(m, "%pi6 %02x ", &rt->rt6i_src.addr, rt->rt6i_src.plen);
-#else
-	seq_puts(m, "00000000000000000000000000000000 00 ");
-#endif
-	if (rt->rt6i_flags & RTF_GATEWAY) {
-		seq_printf(m, "%pi6", &rt->rt6i_gateway);
-	} else {
-		seq_puts(m, "00000000000000000000000000000000");
-	}
-	seq_printf(m, " %08x %08x %08x %08x %8s\n",
-		   rt->rt6i_metric, atomic_read(&rt->dst.__refcnt),
-		   rt->dst.__use, rt->rt6i_flags,
-		   rt->dst.dev ? rt->dst.dev->name : "");
-	return 0;
-}
-
-static int ipv6_route_show(struct seq_file *m, void *v)
-{
-	struct net *net = (struct net *)m->private;
-	fib6_clean_all_ro(net, rt6_info_route, 0, m);
-	return 0;
-}
-
-static int ipv6_route_open(struct inode *inode, struct file *file)
-{
-	return single_open_net(inode, file, ipv6_route_show);
-}
-
 static const struct file_operations ipv6_route_proc_fops = {
 	.owner		= THIS_MODULE,
 	.open		= ipv6_route_open,
 	.read		= seq_read,
 	.llseek		= seq_lseek,
-	.release	= single_release_net,
+	.release	= seq_release_net,
 };
 
 static int rt6_stats_seq_show(struct seq_file *seq, void *v)