KEYS: Make /proc/keys use keyid not numread as file position [try #6]

Make the file position maintained by /proc/keys represent the ID of the key
just read rather than the number of keys read.  This should make it faster to
perform a lookup as we don't have to scan the key ID tree from the beginning to
find the current position.
Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>

security/keys/proc.c

@@ -91,57 +91,90 @@ __initcall(key_proc_init);
  */
 #ifdef CONFIG_KEYS_DEBUG_PROC_KEYS
 
-static struct rb_node *__key_serial_next(struct rb_node *n)
+static struct rb_node *key_serial_next(struct rb_node *n)
 {
+	struct user_namespace *user_ns = current_user_ns();
+
+	n = rb_next(n);
 	while (n) {
 		struct key *key = rb_entry(n, struct key, serial_node);
-		if (key->user->user_ns == current_user_ns())
+		if (key->user->user_ns == user_ns)
 			break;
 		n = rb_next(n);
 	}
 	return n;
 }
 
-static struct rb_node *key_serial_next(struct rb_node *n)
+static int proc_keys_open(struct inode *inode, struct file *file)
 {
-	return __key_serial_next(rb_next(n));
+	return seq_open(file, &proc_keys_ops);
 }
 
-static struct rb_node *key_serial_first(struct rb_root *r)
+static struct key *find_ge_key(key_serial_t id)
 {
-	struct rb_node *n = rb_first(r);
-	return __key_serial_next(n);
-}
+	struct user_namespace *user_ns = current_user_ns();
+	struct rb_node *n = key_serial_tree.rb_node;
+	struct key *minkey = NULL;
 
-static int proc_keys_open(struct inode *inode, struct file *file)
-{
-	return seq_open(file, &proc_keys_ops);
+	while (n) {
+		struct key *key = rb_entry(n, struct key, serial_node);
+		if (id < key->serial) {
+			if (!minkey || minkey->serial > key->serial)
+				minkey = key;
+			n = n->rb_left;
+		} else if (id > key->serial) {
+			n = n->rb_right;
+		} else {
+			minkey = key;
+			break;
+		}
+		key = NULL;
+	}
+
+	if (!minkey)
+		return NULL;
 
+	for (;;) {
+		if (minkey->user->user_ns == user_ns)
+			return minkey;
+		n = rb_next(&minkey->serial_node);
+		if (!n)
+			return NULL;
+		minkey = rb_entry(n, struct key, serial_node);
+	}
 }
 
 static void *proc_keys_start(struct seq_file *p, loff_t *_pos)
 	__acquires(key_serial_lock)
 {
-	struct rb_node *_p;
-	loff_t pos = *_pos;
+	key_serial_t pos = *_pos;
+	struct key *key;
 
 	spin_lock(&key_serial_lock);
 
-	_p = key_serial_first(&key_serial_tree);
-	while (pos > 0 && _p) {
-		pos--;
-		_p = key_serial_next(_p);
-	}
-
-	return _p;
+	if (*_pos > INT_MAX)
+		return NULL;
+	key = find_ge_key(pos);
+	if (!key)
+		return NULL;
+	*_pos = key->serial;
+	return &key->serial_node;
+}
 
+static inline key_serial_t key_node_serial(struct rb_node *n)
+{
+	struct key *key = rb_entry(n, struct key, serial_node);
+	return key->serial;
 }
 
 static void *proc_keys_next(struct seq_file *p, void *v, loff_t *_pos)
 {
-	(*_pos)++;
-	return key_serial_next((struct rb_node *) v);
+	struct rb_node *n;
 
+	n = key_serial_next(v);
+	if (n)
+		*_pos = key_node_serial(n);
+	return n;
 }
 
 static void proc_keys_stop(struct seq_file *p, void *v)